Library Integration is Incomplete

*I'm submitting a ...*
- [x] bug report
- [ ] feature request
- [ ] support request

## General infomration

### Prerequisites

* [x] Are you running the latest version?
0.140.0 PR#519 - https://github.com/asciidisco/plugin.video.netflix/pull/519

### Description

I've configured my Dad's Kodi box (running Kodi 18 beta) with this latest PR to get the added benefits of Netflix Profiles. I can add and remove shows from his "watchlist" just fine. I took it a step further and enabled the library integration. He's never used Kodi's Library functions, so there is nothing to lose by having this not work. But it is a nice feature with better organization and the ability to automatically jump to the next unwatched episode. The problem we seem to be having may be by design, but I don't think so. When he is browsing Netflix, and finds a show he wants to add to his lists, he clicks on the "Add to Watchlist" context button. That works. However, as soon as he triggers it, Kodi takes over and starts downloading the metadata into his library. I thought this was supposed to happen at the specified time in the settings (ie; daily at 23:59:59). Instead, it does it right then and there. On the flip side, removing a show/movie DOESN'T work at all. Sure, he can remove it from the Netflix addon via the "watchlist", but it doesn't remove it from his Kodi Library. We had it run over night to see if it would remove it automatically at midnight.. it didn't. We figured out you can force remove the item from within the Library, but once he reboots the system, it re-integrates it back. I did some digging, and saw that the files the addon creates in the userdata path for library integration don't get erased when they're removed from the library/wishlist. So they will always get re-added. As a temporary fix, I disabled the Kodi setting to check for new files at startup. But that's a bandaid fix. The root problem I think is related to how the Netflix addon is operating it's "remove from watchlist". I thought it should "remove from library" as well. As I said though, this may be by design. But it seems that if you're doing a removal, it should remove EVERYTHING, not just the watchlist entry but also the placeholder files in the userdata folder as well.

### Steps to Reproduce

1. Find a Show
2. Add to Watchlist
3. **1st problem** Show is immediately added to Library, not at it's designated preset time via addon settings.
4. **Behind the scenes** Placeholder files are downloaded in the addon's userdata folder for the Library to integrate.
5. Watch various things, or whatever.
6. Remove a show from watchlist (via Netflix addon).
7. **Behind the scenes** Show is removed from watchlist, but placeholder files are not erased, and the Kodi Library is not updated to show item was removed.
8. Return to Library - Show still exists
9. Reboot - Show still exists
10. Forcibly remove the show from the library - Library updates and it's gone.
11. Reboot - Show is added to the library again (unless "check for new files to add to library on restart" is disabled).

**Expected behavior:** [What you expected to happen]
I'd expect to have a show that I've finished watching or decide to stop watching and remove the Watchlist to also be removed from the Kodi Library

**Actual behavior:** [What actually happened]
The show is removed from the Netflix Watchlist only, remains inside Kodi Library until forcibly removed, then gets readded upon reboot because placeholder files in the userdata folder aren't erased.

## Context (Environment)
Raspberry Pi 3b+, LibreELEC 8.90.006, Kodi Leia 18 beta, This Addon/build 0.14.0 PR-519, Aeon MQ8 v2.1.0 beta Skin

### Installation

* [ ] I installed the plugin via zip from the Releases page
* [ ] I´m using the Netflix Repo
* [x] I´m using a different source (Please tell which)
Installed beta repo zip and installed from that repo.
https://github.com/caphm/kodi-repo/raw/master/repository.kodi-repo-caphm/repository.kodi-repo-caphm-1.0.0.zip

### Operating System

* [ ] Linux (x86/x64)
* [ ] OSX (x86/x64)
* [ ] Windows (x86/x64)
* [x] Linux (ARM)
* [ ] Android

#### Additional informatin on the environment

[Descripe your environment a bit more detailed, are you using LibreElec f.e.]
See Above

## Debug log

[Please include a link to your debug log (use something like [http://sprunge.us/](http://sprunge.us/)) or similar, please do not paste]
I can provide this later if requested. My dad is currently using the device and I won't be able to reproduce to get the debug for a few hours.

## Other information

[e.g. detailed explanation, related issues, suggestions how to fix, links for us to have context, etc.]
See Above - Suggested fix would be to check and erase the placeholder files after removing an item from the watchlist. I assume the nightly Library update (via addon settings) should suffice at removing the show after that.

### Screenshots

[Please add a screenshot if that helps understanding your problem]
I can do one better. If you require further example, I can hook up my camera to a tripod and record a short video of the problem and post it to YouTube.

[You can erase any parts of this template not applicable to your Issue.]

Start by tracing the watchlist removal flow and the library-integration settings, focusing on the userdata placeholder files described in the report. Reproduce adding and removing a show, then verify whether removal cleans up those files and whether the Kodi Library stops re-adding the item after a restart or scheduled update.

Written by the indexing model from the issue text.