Changes how TypeGuard types are checked in subtypes

[sobolevn]

Now two functions are not considered subtypes if:

1. First returns TypeGuard, other returns bool. We respect subtyping direction here. TypeGuard is considered to be subtype of bool
2. First returns TypeGuard[int], second returns TypeGuard[str]

Closes#11307

[sobolevn]

Thanks! Now it should be ready.

[hauntsaninja]

Thank you!

[sobolevn]

Thanks everyone!