Remove JIT icall hashing by address. (mono/mono#14870)

Remove JIT icall hashing by address. (mono/mono#14870)

* Work toward removing JIT icall hashing by address.

* Remove JIT icall hashing by address.

* Cleanup amd64 emit_call use.

* Move MonoJumpInfoTarget to among types, not functions.
If mini.h includes mini-runtime.h, then can move it nearer MonoJumpInfo.
Or if returned by out parameter (pointer) instead of struct by value.
Or pair of out parameters instead of struct.

* Closer to historical semantics, at least to avoid assertion failure, will try to refine in a later PR.

* Remove new comments about partial barriers, I think the comments are wrong and the code is correct (except that lock/unlock probably need to be full barriers, if they are not.)

* PR: Don't worry about size of MonoCallInst.jit_icall_id. Let it be 32 or 64 bits instead of 9.

Commit migrated from https://github.com/mono/mono/commit/c398e19d3515c6bbb6046ed014b2095594a15229