[mypyc] Basic test-only support for i32 and i64 (#13018)
Basic support for arithmetic, bitwise and comparison ops using native
int types i32 and i64. Also support some implicit coercions between
int and native int types. There are still various gaps in the functionality,
and that's why the feature is test-only so far.
Division and modulus ops require jumping through some hoops to make
the behavior with negative operands match Python semantics.
This can already show some improvements in benchmarks (using hacks
these can be used outside tests). I'll post figures once the implementation
is more complete.
Work on mypyc/mypyc#837.
