This removes the majority of `../../../../../../test_util` relative
imports from the codebase, allowing us to move this code more easily in
the future.
Fixes https://github.com/denoland/deno/issues/21734
Changes:
- Use default encode when options do not provide a encode callback.
- Remove internal TS for `node:querystring`. Its not helping catching
bugs like this because of invalid type assumptions and use of `any`,
more of a maintenance burden.
