Change parseList funcs into methods, use method expressions in calls

[jakebailey]

The first commit changes parseList (and siblings) into methods, now that they are not generic anymore after Node was made a struct.

The second switches to using method expression syntax for parseList calls (and others), explicitly passing in p from parseList, which avoids creating a closure object just to re-pass p.

Benchmarks show a slight improvement:

goos: linux
goarch: amd64
pkg: github.com/microsoft/typescript-go/internal/compiler
cpu: Intel(R) Core(TM) i9-10900K CPU @ 3.70GHz
         │   old.txt   │              new.txt               │
         │   sec/op    │   sec/op     vs base               │
Parse-20   45.62m ± 2%   44.59m ± 1%  -2.26% (p=0.000 n=10)

         │   old.txt    │            new.txt             │
         │     B/op     │     B/op      vs base          │
Parse-20   23.59Mi ± 0%   23.59Mi ± 0%  ~ (p=0.796 n=10)

         │   old.txt   │            new.txt            │
         │  allocs/op  │  allocs/op   vs base          │
Parse-20   239.1k ± 0%   239.1k ± 0%  ~ (p=0.809 n=10)