ruleguard/typematch: support func type patterns

[quasilyte]

In addition to basic per-member types, we may want the $*_ to match zero or more members.

func ($*_) $*_ // any kind of function
func ($_) // function of 1 input and 0 outputs
func () $_ // function of 0 inputs and 1 output
func ($*_, int, $*_) int // function that accepts at least 1 int and returns int

[quasilyte]

This was implemented in #82