Add initial Apply UI implementation

[Al12rs]

This PR adds an initial quite rough Apply button implementation.

• Added ApplyService to be used later to queue Apply operations and ensure only one loadout is being applied to a game at a time.
• Added ApplyControlView that contains the Apply and Launch buttons.
• Toggled visibility of buttons based on whether there are things to apply or things are being applied.

So for now the Apply button shows up after the user makes at least one new Loadout revision since starting the app.
Pressing the button Applies the loadout while showing a spinner and hiding the Launch button.
After applying is done the button is hidden waiting for new loadout changes.

Limitations of this PR:

• We currently don't save the last applied Loadout or the last applied Loadout revision, which is necessary to determine whether there are things that need to be applied or not (see Deploying one loadout triggers an ingestion in another loadout #871 for details).
• Currently the newest loadout revision on startup is used as the last applied revision arbitrarily.
• Likewise the number of changes (loadout revisions) to be applied is currently not available.
• In this implementation Apply always ingests outside changes on top of the latest version of the loadout.
• Launch button currently still applies (main reason is that we want to do an ingest after the program returns).
• Ui design for the button only vaguely matches the ones on figma for now.

All of these limitations should be handled after event sourcing has been integrated, together with #871

[erri120]

See comments.

[codecov-commenter]

Codecov Report

Attention: 98 lines in your changes are missing coverage. Please review.

Comparison is base (8728b65) 0.00% compared to head (3387fc8) 58.18%.

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Additional details and impacted files

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Flag	Coverage Δ
Linux	57.44% <2.97%> (?)
Windows	57.39% <2.97%> (?)
clean_environment_tests	58.16% <2.97%> (?)
macOS	56.83% <2.97%> (?)

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Files	Coverage Δ
src/NexusMods.App.UI/Services.cs	98.51% <100.00%> (ø)
src/NexusMods.DataModel/Services.cs	100.00% <100.00%> (ø)
...pp.UI/LeftMenu/Loadout/LoadoutLeftMenuViewModel.cs	0.00% <0.00%> (ø)
...LeftMenu/Loadout/LoadoutLeftMenuDesignViewModel.cs	0.00% <0.00%> (ø)
...p.UI/LeftMenu/Items/ApplyControlDesignViewModel.cs	0.00% <0.00%> (ø)
src/NexusMods.DataModel/ApplyService.cs	0.00% <0.00%> (ø)
...ods.App.UI/LeftMenu/Items/ApplyControlViewModel.cs	0.00% <0.00%> (ø)

... and 630 files with indirect coverage changes