Cleanup of `Io` module.
Cleanup of `Io` module.

  - Undid rename from `Io` to `IO`
  - Ensured function signatures in comments have leading `func`
  - Removed superfluous `extends Function` clauses
  - Renamed a few classes to be more consistent.

github/codeql,github/codeql,github/codeql-go,github/codeql,github/codeql,github/codeql,github/codeql,github/codeql,github/codeql-go,github/codeql,github/codeql-go,github/codeql,github/codeql,github/codeql,github/codeql,github/codeql,github/codeql,github/codeql,github/codeql-go