Support callable literal syntax

[KotlinIsland]

a: "(int) -> str"
reveal_type(a) # (int) -> str

please 😊

[DetachHead]

imo types that need to be in quotes look gross. would prefer something that works at runtime, and ideally something that also addresses #20

[DetachHead]

looks like pyright used to support this because it was in a rejected pep. we can probably just revert 9949577cedc108274204f9bf58f6f207b63ac1d2