plugins: List disabled and not loaded plugins

[Penwy]

Description

This does two things :

• List the plugins disabled through the plugin manager in the installed plugins list, marked as (disabled).
• List any of the plugins that failed to load.

Failing to load in the manner listed here can, as far as I know happen in three cases :

• Libobs incompatibility when the plugin uses a symbol that does not exist in the running version of libobs
• Libobs incompatibility when the plugin is compiled for a version of it more recent than the running one
• Missing dependency for the plugin.

Motivation and Context

Both those information can be useful for the user to know.

How Has This Been Tested?

Ran manually with those three logs :

• 1 : from support, disabled plugin
• 2 : from support, removed symbol.
• 3 : artificially created by Sebastian, compiled with newer libobs.

Types of changes

• New feature (non-breaking change which adds functionality)
• Tweak (non-breaking change to improve existing functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[prgmitchell]

looks good, did some testing myself and it seems fine.

I am just not sure if a plugin not loading needs to be listed as critical, I personally think it should be a warning.

[Penwy]

I kept the critical from the outdated plugins warning, since not loaded would inherit outdated plugins, but yeah, that is likely a bit much, will change when I get around to it.