Optimize len for string constants in optimizer

[y1yang0]

Feature or enhancement

Proposal:

Hi team, I found an optimization opportunity: len() calls on string constants can be
optimized at compile time, similar to how tuple constants are handled.

Quick testing with python -m test showed _CALL_LEN hits:

• str: 23 (6 optimizable with this patch)
• list: 28
• tuple: 4 (3 already optimized)

This patch extends the existing constant folding for len(tuple) to also handle
len("string"), replacing the function call with _SHUFFLE_3_LOAD_CONST_INLINE_BORROW
when the result is an immortal integer.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-144140: Optimize len for string constants in optimizer #144142
• gh-144140: Optimize len for frozen dict/set constants in optimizer #149969