codegen: handle dbg_var scoping correctly after eliding more ZIR blocks

Since we now elide more ZIR blocks in AstGen, care must be taken in
codegen to introduce lexical scopes for every body, not just `block`s.

Also, elide a few unnecessary AIR blocks in Sema.
321045cf33mlugg committed on 2/29/2024, 11:38:18 PMparentf51d9ab
2 files changedLine totals unavailable