fix: re-register dotnet for core22

[mr-cal]

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• re-register dotnet for core22
• add core22 and core24 dotnet spread tests
• refactor Application to allow snapcraft to register/unregister plugins per-base
  • this includes renaming _known_core24 to _known_craft_app_base in preparation for core26

Fixes #4825
(CRAFT-2979)

[mr-cal]

Force-pushed because I dropped all changes related to running the ClassicFallback or craft-application based codepath.

It's too disruptive of a change for a hotfix.

[cmatsuoka]

We can generalize the calls a bit more instead of being core24-specific in a future refactoring, but this solves the reported issue.

[mr-cal]

We can generalize the calls a bit more instead of being core24-specific in a future refactoring, but this solves the reported issue.

Agreed. In a point release, we should flip the paradigm such that the craft-application codepath is used by default and Snapcraft only raises ClassicFallback if we know we should use the core20 or core22 feature set.