[clang] [llvm] [analyzer] Remove the alpha.core.FixedAddr checker (PR #182033)

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat approved this pull request.

The checker `optin.core.FixedAddressDereference` was developed (by @balazske) with the goal that it will supersede this old alpha checker to make this removal possible.

The change LGTM assuming that you checked the results of `git grep FixedAddr` (or equivalent).

https://github.com/llvm/llvm-project/pull/182033