check non-callable __bool__ on in operator result

[knQzx]

summary

• in/not in operator now checks that bool is callable on the contains return type
• also returns bool instead of the raw contains return type, matching python semantics

test plan

• updated existing bug test case to expect the error
• all 4678 tests pass

fixes #2913

[github-actions]

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