feat: constant fold common builtin call expressions [3/3]

[BobTheBuidler]

This PR implements constant folding for builtin callables where possible.

If all args are constant foldable and the callable is one of the builtin callables below, mypy can, in most cases, fold the result.

The supported builtins are:

foldable_builtins = {
    "builtins.str": str,
    "builtins.int": int,
    "builtins.bool": bool,
    "builtins.float": float,
    "builtins.complex": complex,
    "builtins.repr": repr,
    "builtins.len": len,
    "builtins.hasattr": hasattr,
    "builtins.hex": hex,
    "builtins.min": min,
    "builtins.max": max,
    "builtins.oct": oct,
    "builtins.pow": pow,
    "builtins.round": round,
    "builtins.abs": abs,
    "builtins.ascii": ascii,
    "builtins.bin": bin,
    "builtins.chr": chr,
}

While this PR does not build off of #19885, it does need to come afterward because it contains a refactoring that moves around the code introduced in 19885.

[BobTheBuidler]

I think this might indicate a bug in mypy itself? I don't think this should change just from the constant folding

[BobTheBuidler]

One example of where this would be useful: mypyc/mypyc#1152

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅