Move duplicate `LOAD_SMALL_INT` optimization from codegen to CFG

[WolframAlph]

Feature or enhancement

Proposal:

Addressing #129568 (comment)

Currently both codegen & peepholer optimize LOAD_CONST for small integers to LOAD_SMALL_INT. CFG can do it alone, so we don't have this logic in 2 places.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-130480: Move duplicate LOAD_SMALL_INT optimization from codegen to CFG #130481