chore(python): clean up bytecode parsing a bit

[MarcoGorelli]

There's 3 cleanups I'm suggesting here:

1. make try blocks smaller. I think this is uncontroversial

2. remove an unused try block in _is_raw_function. The whole test suite passes without it, I think it the code can be simplified by just removing it

3. removing the _can_attempt_rewrite dict. I think this was originally introduced for performance reasons, but:

   • I'm not seeing any perf difference here vs on main (timing pl.col('a').map_elements(lambda x: abs(x)) here and on main takes about 8.988900013459247e-05 seconds on my laptop
   • it adds quite a lot of complexity

   It's already super-fast, I don't think the extra complexity is warranted

[MarcoGorelli]

@alexander-beedie fancy taking a look?

[alexander-beedie]

@alexander-beedie fancy taking a look?

Definitely! Can dig in tonight (or tomorrow morning) and see if I can recall the primary scenario this speeds up (or used to speed up 😂)