.sln files in sub folders take precedence over root .csproj file

Type: Bug

## Issue Description ##
I have a .csproj file in the root folder, which is the relevant one I want to use. This main project also doesn't have an .sln file.

For reference, I also keep source files of used (and slightly modified) 3rd party libraries including its VS .sln files in sub folders, but they are not relevant for me when I open the root folder for my main solution.


When I start VS Code with this project, the C# extension asks to select a solution file, and fully ignores the .csproj file in the root folder that would actually be relevant. Previously with older versions of the C# extension and/or OmniSharp being used this hasn't been a problem, but now it is.


Due to this I cannot really use the IDE with this project:

## Steps to Reproduce ##
Create a folder structure with a .csproj file in the root folder and unrelated .sln files in a sub directory.

## Expected Behavior ##
The extension already detects that there are multiple project files in the folder structure, the list of project files to select should include .csproj and .sln files.

## Actual Behavior ##
Only .sln files are offered for selection.

## Logs ##

### C# log ###
Using dotnet configured on PATH
Dotnet path: C:\Program Files\dotnet\dotnet.exe
Activating C# standalone...
waiting for named pipe information from server...
[stdout] {"pipeName":"\\\\.\\pipe\\aeabb6d8-3ada-4d40-ad7a-1b233d3ab3ff"}
received named pipe information from server
attempting to connect client to server...
client has connected to server
[Info - 4:01:44 PM] [Program] Language server initialized
Using dotnet configured on PATH

## Environment information ##

**VSCode version**: 1.82.2
**C# Extension**: 2.4.4
**Using OmniSharp**: false

Dotnet Information
.NET SDK:
Version: 7.0.401
Commit: eb26aacfec

Runtime Environment:
OS Name: Windows
OS Version: 10.0.22631
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\7.0.401\

Host:
Version: 7.0.11
Architecture: x64
Commit: ecb34f85ec

.NET SDKs installed:
5.0.416 [C:\Program Files\dotnet\sdk]
6.0.414 [C:\Program Files\dotnet\sdk]
7.0.401 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.22 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.22 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.22 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]

Environment variables:
Not set

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download

Visual Studio Code Extensions

|Extension|Author|Version|Folder Name|
|---|---|---|---|
|add-reference|adrianwilczynski|1.0.2|adrianwilczynski.add-reference-1.0.2|
|azure-repos|ms-vscode|0.36.0|ms-vscode.azure-repos-0.36.0|
|batch-runner|NilsSoderman|1.1.2|nilssoderman.batch-runner-1.1.2|
|Bookmarks|alefragnani|13.4.1|alefragnani.bookmarks-13.4.1|
|cmake|twxs|0.0.17|twxs.cmake-0.0.17|
|cmake-tools|ms-vscode|1.15.31|ms-vscode.cmake-tools-1.15.31|
|copilot|GitHub|1.121.456|github.copilot-1.121.456|
|copilot-chat|GitHub|0.7.1|github.copilot-chat-0.7.1|
|copilot-labs|GitHub|0.15.1019|github.copilot-labs-0.15.1019|
|cpptools|ms-vscode|1.17.5|ms-vscode.cpptools-1.17.5-win32-x64|
|cpptools-extension-pack|ms-vscode|1.3.0|ms-vscode.cpptools-extension-pack-1.3.0|
|cpptools-themes|ms-vscode|2.0.0|ms-vscode.cpptools-themes-2.0.0|
|csharp|ms-dotnettools|2.4.4|ms-dotnettools.csharp-2.4.4-win32-x64|
|csharpextensions|kreativ-software|1.7.3|kreativ-software.csharpextensions-1.7.3|
|discord-vscode|icrawl|5.8.0|icrawl.discord-vscode-5.8.0|
|docomment|k--kato|1.0.0|k--kato.docomment-1.0.0|
|EditorConfig|EditorConfig|0.16.4|editorconfig.editorconfig-0.16.4|
|github-markdown-preview|bierner|0.3.0|bierner.github-markdown-preview-0.3.0|
|gitlens|eamodio|14.3.0|eamodio.gitlens-14.3.0|
|jupyter|ms-toolsai|2023.8.1002501831|ms-toolsai.jupyter-2023.8.1002501831-win32-x64|
|jupyter-keymap|ms-toolsai|1.1.2|ms-toolsai.jupyter-keymap-1.1.2|
|jupyter-renderers|ms-toolsai|1.0.17|ms-toolsai.jupyter-renderers-1.0.17|
|luahelper|yinfei|0.2.24|yinfei.luahelper-0.2.24|
|makefile-tools|ms-vscode|0.7.0|ms-vscode.makefile-tools-0.7.0|
|markdown-checkbox|bierner|0.4.0|bierner.markdown-checkbox-0.4.0|
|markdown-emoji|bierner|0.3.0|bierner.markdown-emoji-0.3.0|
|markdown-footnotes|bierner|0.1.1|bierner.markdown-footnotes-0.1.1|
|markdown-mermaid|bierner|1.20.0|bierner.markdown-mermaid-1.20.0|
|markdown-preview-github-styles|bierner|2.0.3|bierner.markdown-preview-github-styles-2.0.3|
|markdown-yaml-preamble|bierner|0.1.0|bierner.markdown-yaml-preamble-0.1.0|
|nsis|idleberg|4.2.4|idleberg.nsis-4.2.4|
|nugetpackagemanagergui|aliasadidev|2.0.6|aliasadidev.nugetpackagemanagergui-2.0.6|
|powershell|ms-vscode|2023.6.0|ms-vscode.powershell-2023.6.0|
|python|ms-python|2023.16.0|ms-python.python-2023.16.0|
|remote-repositories|ms-vscode|0.38.1|ms-vscode.remote-repositories-0.38.1|
|remote-wsl|ms-vscode-remote|0.81.7|ms-vscode-remote.remote-wsl-0.81.7|
|remotehub|GitHub|0.60.0|github.remotehub-0.60.0|
|rss|luyuhuang|0.10.4|luyuhuang.rss-0.10.4|
|todo-tree|Gruntfuggly|0.0.226|gruntfuggly.todo-tree-0.0.226|
|vscode-autohotkey-plus-plus|mark-wiemer|5.0.3|mark-wiemer.vscode-autohotkey-plus-plus-5.0.3|
|vscode-counter|uctakeoff|3.2.1|uctakeoff.vscode-counter-3.2.1|
|vscode-dotnet-runtime|ms-dotnettools|1.8.0|ms-dotnettools.vscode-dotnet-runtime-1.8.0|
|vscode-guid|heaths|1.7.0|heaths.vscode-guid-1.7.0|
|vscode-gutter-preview|kisstkondoros|0.30.0|kisstkondoros.vscode-gutter-preview-0.30.0|
|vscode-jupyter-cell-tags|ms-toolsai|0.1.8|ms-toolsai.vscode-jupyter-cell-tags-0.1.8|
|vscode-jupyter-slideshow|ms-toolsai|0.1.5|ms-toolsai.vscode-jupyter-slideshow-0.1.5|
|vscode-pylance|ms-python|2023.9.30|ms-python.vscode-pylance-2023.9.30|
|xml|DotJoshJohnson|2.5.1|dotjoshjohnson.xml-2.5.1|;

Extension version: 2.4.4
VS Code version: Code 1.82.2 (abd2f3db4bdb28f9e95536dfa84d8479f1eb312d, 2023-09-14T05:55:25.390Z)
OS version: Windows_NT x64 10.0.22631
Modes:

System Info

|Item|Value|
|---|---|
|CPUs|AMD Ryzen 5 7640U w/ Radeon 760M Graphics (12 x 3493)|
|GPU Status|2d_canvas: enabled
canvas_oop_rasterization: enabled_on
direct_rendering_display_compositor: disabled_off_ok
gpu_compositing: enabled
multiple_raster_threads: enabled_on
opengl: enabled_on
rasterization: enabled
raw_draw: disabled_off_ok
video_decode: enabled
video_encode: enabled
vulkan: disabled_off
webgl: enabled
webgl2: enabled
webgpu: enabled|
|Load (avg)|undefined|
|Memory (System)|12.73GB (3.99GB free)|
|Process Argv|--crash-reporter-id 6fb09b72-737b-406a-9aff-30d009da46b7|
|Screen Reader|no|
|VM|0%|

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