JIT: remove incremental ref count updates (dotnet/coreclr#19345)

JIT: remove incremental ref count updates (dotnet/coreclr#19345)

Remove almost all of the code in the jit that tries to maintain local ref
counts incrementally. Also remove `lvaSortAgain` and related machinery.

Explicitly sort locals before post-lower-liveness when optimizing to get the
best set of tracked locals.

Explicitly recount after post-lower liveness to get accurate counts after
dead stores. This can lead to tracked unreferenced arguments; tolerate this
during codegen.

Commit migrated from https://github.com/dotnet/coreclr/commit/895bfa452da4aeeda52447e76d9e9e987d68f331