refactor(ci): Review the mutation testing workflow

[theofidry]

My understanding of that build was, from what I understand in #1365, to have a dedicated pipeline mimicking what a typical user pipeline may look like and testing our mutation badge feature. Over time this was slightly tweaked:

• The test for windows was removed because overly slow (Do not run Infection for itself on windows #1611)
• Remove testing against different dependencies (Run Infection on PHP 8.1. #1535) – Likely due to instability in the build

I think the build is still useful, but we now have a more comprehensive and diversified test suite to test the different OS, dependencies, code coverage reports and co in ci.yaml. Hence this build can be more scoped and from that simplified.

• Document the above in the build
• Bump the PHP version to 8.2
• Use the locked version of the dependencies
• Use the latest Composer version available

Tried to switch to Xdebug. I was curious if there is a big time difference but in general I also know Xdebug is more accurate than pcov, so we may prefer this to enforce a specific MSI score.

Comparing with this build, we had:

	pcov	Xdebug	delta
time taken (unit tests)	1m7	1m34	+40%
time taken (infection)	8m7	13m41	+70%
MSI	73%		75%

At least from those results it doesn't look worth it.

⚠️ Requires to update the project settings afterwards as the build name changes

[maks-rafalko]

why is it needed?

[theofidry]

Because depending on the deprecations it can fail this build. It's not necessarily bad, but we already check for the deprecations in ci.yaml. So having it here is redundant, and disabling it guaranteeing we get to the interesting part of that build which is running infection with coverage generated and with the badge API key

[theofidry]

Lemme know if that's a satisfying answer for you or you prefer to keep it