Following the split of the compiler into 3 parts in #87092, the resolution of jump targets is still in the optimizer, but it should move to the assembler.

There are also a few operations in compile.c that could move into the optimizer.

Linked PRs

• gh-106149: move jump target resolution from optimizer to assembler #106150
• gh-106149: move unconditional jump direction resolution from optimizer to assembler #106291
• gh-106149: move _PyCfg_BasicblockLastInstr and make it local to flowgraph.c #107180
• gh-106149: Simplify stack depth calculation. Replace asserts by exceptions. #107255
• gh-106149: fix comment on stackdepth of generators #107321
• gh-106149: move CFG and basicblock definitions into flowgraph.c, use them as opaque types in compile.c #107639