doc: refactor fs docs structure

* Convert examples to esm to help promote that pattern with users
* Make Promises APIs more prominent to help promite that pattern
* Separate callback/sync apis into distinct sections to make those
  more consistent with the Promises api
* Improve other bits and pieces

Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: #37170
Backport-PR-URL: #39706
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/dgram.md

@@ -733,6 +733,9 @@ chained.
 <!-- YAML
 added: v0.11.13
 changes:
+  - version: v14.17.0
+    pr-url: https://github.com/nodejs/node/pull/37026
+    description: AbortSignal support was added.
   - version: v11.4.0
     pr-url: https://github.com/nodejs/node/pull/23798
     description: The `ipv6Only` option is supported.