updater: Check if awaited instance matches current install

[derrod]

Description

When checking for running OBS instance ensure the executable of an OBS process is actually residing the the directory we want to update.

Based on an old WIP commit: https://github.com/notr1ch/obs-studio/commit/95909ee25c3bbab9f6adc2a5c3795b0c115dd185

Note: This PR includes #8141 to avoid writing code that would get immediately thrown away once that is merged. It's a draft because of that.

Motivation and Context

Allow updating OBS even if some other obs64.exe is running (e.g. updating portable install while non-portable version is running).

Also selfishly, this means I won't have to use ShareX when recording my screen while working on updater updates :P

How Has This Been Tested?

Verified portable install can be updated while existing OBS install is running

Types of changes

• Tweak (non-breaking change to improve existing functionality)

Checklist:

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