Add binder benchmark, update parse benchmark, restructure fixtures

[jakebailey]

• Add a binder benchmark
• Fix up the parser benchmark to call the right error method
• Consolidate test file reading into one place with skips
• Remove need for submodule checkout to run tests; tests which read the TS repo can just t.Skip.
• Benchmark multiple input files

Running a specific benchmark looks like:

$ go test -run=- -bench=BenchmarkParse/checker.ts -benchmem ./internal/compiler