Motivation:
str interning for a long running python program could use a lot of memory
our current implementation is also not quite the same as cpython

Our constants are cached during compilation so tests that look for compiled str identity will still work
I actually didn't need to change any tests here.

I adjusted places where we rely on str identity in the code base

This reliance also meant implementing tp$hash for Sk.builtin.str
(The python 2.7 implementation is much easier to follow so I used that)

I adjusted the internals of $name for Sk.builtin.func to be a python string.
There was a test for this in test_functools that expected __name__ to be identical after wrapping