Fix AlertListener on IPv6-aware hosts and prevent YoutubeDL from making the plugin hang

[zdimension]

Description

• on many Linux machines, localhost resolves to ::1. The websocket module used here expects an AF_INET address, so it expectedly crashes when passed an IPv6 address such as ::1. The default URL used for reaching Plex is modified to 127.0.0.1 to prevent this.
• no code was present to handle YoutubeDL raising an exception. If such a case were to happen previously, the whole thread would crash; in practice this means that if any movie in the library can't be downloaded for any reason, the worker thread trying to download it will crash and stop processing any more content. In the worst case (e.g. mine) you can end up with all threads hung. Refreshing metadata or restarting the plugin doesn't change anything, the problem is logical and deterministic. Errors are now handled properly and printed to the plugin logs, and the process can continue.
• also, a typo in the YoutubeDL call is fixed (outmpl -> outtmpl)

Issues Fixed or Closed

• Fixes AlertListener does not work with some hosts on Linux #143
• Fixes youtube-dl logs are going to system/container log #163

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update (updates to dependencies)
• Documentation update (changes to documentation)
• Repository update (changes to repository files, e.g. .github/...)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the in code docstring/documentation-blocks for new or existing methods/components

Branch Updates

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must be updated before it can be merged. You must also
Allow edits from maintainers.

• I want maintainers to keep my branch updated

[CLAassistant]

All committers have signed the CLA.

[ReenigneArcher]

Thanks for the PR!

There's a simpler way to use the plugin logger.

Can you think of some way to force/test this exception situation?

[codecov]

Codecov Report

Merging #196 (b7ecf58) into nightly (15099a5) will increase coverage by 0.24%.
The diff coverage is 90.90%.

❗ Current head b7ecf58 differs from pull request most recent head 85dc094. Consider uploading reports for the commit 85dc094 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           nightly     #196      +/-   ##
===========================================
+ Coverage    68.97%   69.22%   +0.24%     
===========================================
  Files           10       10              
  Lines          735      744       +9     
===========================================
+ Hits           507      515       +8     
- Misses         228      229       +1     

Flag	Coverage Δ
Linux	69.22% <90.90%> (+0.24%)	⬆️
Windows	27.82% <36.36%> (-37.90%)	⬇️
macOS	27.82% <36.36%> (-41.16%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
Contents/Code/plex_api_helper.py	53.28% <100.00%> (ø)
Contents/Code/youtube_dl_helper.py	86.00% <90.00%> (+0.63%)	⬆️