test: split test-whatwg-encoding-textdecoder-fatal.js

Split `test-whatwg-encoding-textdecoder-fatal.js` into

- `test-whatwg-encoding-custom-textdecoder-fatal.js` which
  is a customized version of the WPT that tests for Node.js-specific
  error codes.
- `test-whatwg-encoding-custom-textdecoder-invalid-arg` which
  tests `ERR_INVALID_ARG_TYPE`

PR-URL: https://github.com/nodejs/node/pull/25155


Reviewed-By: James M Snell <jasnell@gmail.com>