Creating graph edges individually doesn't show animation

Nobody has claimed this yet.

## Description of bug / unexpected behavior

I'm trying to change how the timing of a graph's edges and vertices are created so that graphs with many edges have an equal amount of time spend created edges and vertices. When I create the edges in an `AnimationGroup`, nothing is shown on the screen but the edges then all appear at once after the animation is over.

## Expected behavior

The edges should appear one at a time, just like the vertices.

## How to reproduce the issue

Code for reproducing the problem

```py
from manim import *

class TestScene(Scene):
def construct(self):
graph = Graph(
vertices=[1, 2, 3, 4, 5],
edges=[
(1, 2),
(1, 3),
(1, 4),
(1, 5),
(2, 3),
(2, 4),
(2, 5),
(3, 4),
(3, 5),
(4, 5),
],
vertex_type=Circle,
vertex_config={"radius": 0.25},
)
# default behavior; edges are created one at a time
self.play(Create(graph), run_time=4)
self.clear()
# manually created the vertices, works as expected
self.play(
AnimationGroup(
*(Create(vertex) for vertex in graph.vertices.values()),
lag_ratio=0.1,
),
run_time=2,
)
# manually create the edges, edges appear all at once?
self.play(
AnimationGroup(
*(Create(edge) for edge in graph.edges.values()),
lag_ratio=0.1,
),
run_time=2,
)
self.pause(3)

```

## Additional media files

Images/GIFs

https://github.com/ManimCommunity/manim/assets/90520516/500dfcbf-f9ff-4dff-9d4c-acee665d0d1f

## Logs
Terminal output

```
> manim -pqh -v DEBUG test.py TestScene

Manim Community v0.18.0

[01/18/24 18:23:59] DEBUG Hashing ... hashing.py:350
DEBUG Hashing done in 0.016427 s. hashing.py:362
DEBUG Hash generated : 3529212410_466792430_223132457 hashing.py:365
DEBUG List of the first few animation hashes of the scene: cairo_renderer.py:87
['3529212410_466792430_223132457']
Animation 0: Create(Undirected graph on 5 vertices and 10 edges): 30%|####5 | 73/240 [00:01<00:02, 56.22it/s]
(process:3544): GLib-GIO-WARNING **: 18:24:01.080: Unexpectedly, UWP app `Microsoft.ScreenSketch_11.2310.54.0_x64__8wekyb3d8bbwe' (AUMId `Microsoft.ScreenSketch_8wekyb3d8bbwe!App') supports 29 extensions but has no verbs
Animation 0: Create(Undirected graph on 5 vertices and 10 edges): 33%|####9 | 79/240 [00:01<00:02, 56.13it/s]
(process:3544): GLib-GIO-WARNING **: 18:24:01.155: Unexpectedly, UWP app `Microsoft.OutlookForWindows_1.2023.1214.201_x64__8wekyb3d8bbwe' (AUMId `Microsoft.OutlookForWindows_8wekyb3d8bbwe!Microsoft.OutlookforWindows') supports 1 extensions but has no verbs
[01/18/24 18:24:04] INFO Animation 0 : Partial movie file written in scene_file_writer.py:527
'D:\ml-visualize\media\videos\test\1080p60\partial_movie_files\Tes
tScene\3529212410_466792430_223132457.mp4'
DEBUG Hashing ... hashing.py:350
DEBUG Hashing done in 0.008106 s. hashing.py:362
DEBUG Hash generated : 3040924799_2563770218_2358810818 hashing.py:365
DEBUG List of the first few animation hashes of the scene: cairo_renderer.py:87
['3529212410_466792430_223132457', '3040924799_2563770218_2358810818']
[01/18/24 18:24:05] INFO Animation 1 : Partial movie file written in scene_file_writer.py:527
'D:\ml-visualize\media\videos\test\1080p60\partial_movie_files\Tes
tScene\3040924799_2563770218_2358810818.mp4'
DEBUG Hashing ... hashing.py:350
DEBUG Hashing done in 0.022348 s. hashing.py:362
DEBUG Hash generated : 3040924799_738277517_2459790260 hashing.py:365
DEBUG List of the first few animation hashes of the scene: cairo_renderer.py:87
['3529212410_466792430_223132457', '3040924799_2563770218_2358810818',
'3040924799_738277517_2459790260']
[01/18/24 18:24:07] INFO Animation 2 : Partial movie file written in scene_file_writer.py:527
'D:\ml-visualize\media\videos\test\1080p60\partial_movie_files\Tes
tScene\3040924799_738277517_2459790260.mp4'
DEBUG Animation with empty mobject animation.py:174
DEBUG Hashing ... hashing.py:350
DEBUG Hashing done in 0.019766 s. hashing.py:362
DEBUG Hash generated : 3040924799_2475379470_3097048898 hashing.py:365
DEBUG List of the first few animation hashes of the scene: cairo_renderer.py:87
['3529212410_466792430_223132457', '3040924799_2563770218_2358810818',
'3040924799_738277517_2459790260', '3040924799_2475379470_3097048898']
[01/18/24 18:24:09] INFO Animation 3 : Partial movie file written in scene_file_writer.py:527
'D:\ml-visualize\media\videos\test\1080p60\partial_movie_files\Tes
tScene\3040924799_2475379470_3097048898.mp4'
INFO Combining to Movie file. scene_file_writer.py:617
DEBUG Partial movie files to combine (4 files): scene_file_writer.py:561
['D:\\ml-visualize\\media\\videos\\test\\1080p60\\partial_movie_fi
les\\TestScene\\3529212410_466792430_223132457.mp4',
'D:\\ml-visualize\\media\\videos\\test\\1080p60\\partial_movie_fil
es\\TestScene\\3040924799_2563770218_2358810818.mp4',
'D:\\ml-visualize\\media\\videos\\test\\1080p60\\partial_movie_fil
es\\TestScene\\3040924799_738277517_2459790260.mp4',
'D:\\ml-visualize\\media\\videos\\test\\1080p60\\partial_movie_fil
es\\TestScene\\3040924799_2475379470_3097048898.mp4']
INFO scene_file_writer.py:735
File ready at
'D:\ml-visualize\media\videos\test\1080p60\TestScene.mp4'

INFO Rendered TestScene scene.py:241
Played 4 animations
INFO Previewed File at: file_ops.py:227
'D:\ml-visualize\media\videos\test\1080p60\TestScene.mp4'
```

## System specifications

System Details

- OS: Windows 11 Pro 10.0.22631 Build 22631
- RAM: 16 GB DDR4
- Python version: Python 3.11.5 in venv
- Installed modules (provide output from `pip list`):
```
> pip list

Package Version
---------------------------- ------------
absl-py 2.0.0
astunparse 1.6.3
black 23.12.1
cachetools 5.3.2
certifi 2023.11.17
charset-normalizer 3.3.2
click 8.1.7
click-default-group 1.2.4
cloup 2.1.2
colorama 0.4.6
contourpy 1.2.0
cycler 0.12.1
decorator 5.1.1
flatbuffers 23.5.26
fonttools 4.47.2
gast 0.5.4
glcontext 2.5.0
google-auth 2.26.2
google-auth-oauthlib 1.2.0
google-pasta 0.2.0
grpcio 1.60.0
h5py 3.10.0
idna 3.6
isosurfaces 0.1.0
keras 2.15.0
kiwisolver 1.4.5
libclang 16.0.6
manim 0.18.0
ManimPango 0.5.0
mapbox-earcut 1.0.1
Markdown 3.5.2
markdown-it-py 3.0.0
MarkupSafe 2.1.3
matplotlib 3.8.2
mdurl 0.1.2
ml-dtypes 0.2.0
moderngl 5.9.0
moderngl-window 2.4.4
multipledispatch 1.0.0
mypy-extensions 1.0.0
networkx 3.2.1
numpy 1.26.3
oauthlib 3.2.2
opt-einsum 3.3.0
packaging 23.2
pandas 2.1.4
pathspec 0.12.1
Pillow 9.5.0
pip 23.3.2
platformdirs 4.1.0
protobuf 4.23.4
pyasn1 0.5.1
pyasn1-modules 0.3.0
pycairo 1.25.1
pydub 0.25.1
pyglet 2.0.10
Pygments 2.17.2
pyparsing 3.1.1
pyrr 0.10.3
python-dateutil 2.8.2
pytz 2023.3.post1
requests 2.31.0
requests-oauthlib 1.3.1
rich 13.7.0
rsa 4.9
scipy 1.11.4
screeninfo 0.8.1
setuptools 65.5.0
six 1.16.0
skia-pathops 0.7.4
srt 3.5.3
svgelements 1.9.6
tensorboard 2.15.1
tensorboard-data-server 0.7.2
tensorflow 2.15.0
tensorflow-estimator 2.15.0
tensorflow-intel 2.15.0
tensorflow-io-gcs-filesystem 0.31.0
termcolor 2.4.0
tqdm 4.66.1
typing_extensions 4.9.0
tzdata 2023.4
urllib3 2.1.0
watchdog 3.0.0
Werkzeug 3.0.1
wheel 0.42.0
wrapt 1.14.1
```

FFMPEG

Output of `ffmpeg -version`:

```
> ffmpeg -version

ffmpeg version 6.0-full_build-www.gyan.dev Copyright (c) 2000-2023 the FFmpeg developers
built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libvpl --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
libavutil 58. 2.100 / 58. 2.100
libavcodec 60. 3.100 / 60. 3.100
libavformat 60. 3.100 / 60. 3.100
libavdevice 60. 1.100 / 60. 1.100
libavfilter 9. 3.100 / 9. 3.100
libswscale 7. 1.100 / 7. 1.100
libswresample 4. 10.100 / 4. 10.100
libpostproc 57. 1.100 / 57. 1.100
```

## Additional comments

The graph classes (`GenericGraph`, `Graph`, and `DiGraph`) all set the `z_index` of the edges to be `-1` on creation. Removing this seems to fix the issue, but I don't know why they are there and the full effects of removing them.

https://github.com/ManimCommunity/manim/blob/68bd79093e1ebc1ed9f8051942ffe6e72a9e66a7/manim/mobject/graph.py#L775
https://github.com/ManimCommunity/manim/blob/68bd79093e1ebc1ed9f8051942ffe6e72a9e66a7/manim/mobject/graph.py#L1277
https://github.com/ManimCommunity/manim/blob/68bd79093e1ebc1ed9f8051942ffe6e72a9e66a7/manim/mobject/graph.py#L1479

Run the supplied TestScene reproduction with Python and inspect how Graph, AnimationGroup, and Create handle graph vertices versus edges. The work is done when individually created edges visibly animate one at a time, matching the vertex behavior, while the existing graph creation behavior remains intact.

Written by the indexing model from the issue text.