doc: anchor link parity between markdown and html-generated docs

Main changes:

- Replace current HTML anchor generation to match
  header anchor generation in Github markdown.
- Remove unnecessary double namespacing on generated anchors/links (E.G.
  `esm.md#loaders` instead of `esm.md#esm_loaders`).
- Anchors/links are automatically prefixed with their respective modules
  when concatenated for usage in `all.html`.

Benefits:

- All anchor links within and between markdown API docs actually work.
- Adding new anchor links no longer requires contributors to generate
  the HTML docs first to look up the correct anchors.
- Anchors are much shorter.
- All previous anchor links are preserved by generating hidden legacy
  anchors.

PR-URL: https://github.com/nodejs/node/pull/39304
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

doc/api/string_decoder.md

@@ -92,4 +92,4 @@ Returns a decoded string, ensuring that any incomplete multibyte characters at
  returned string and stored in an internal buffer for the next call to
  `stringDecoder.write()` or `stringDecoder.end()`.
 
-[encoding]: buffer.md#buffer_buffers_and_character_encodings
+[encoding]: buffer.md#buffers-and-character-encodings