S3FileSystem.info() does not use cached directory listings

[laughingman7743]

Problem

S3FileSystem.info() cannot use the directory listings that _ls_dirs() caches.
_ls_dirs() stores listings under (path, delimiter) tuple keys (pyathena/filesystem/s3.py:435, s3.py:472 on master e0e85da), but _ls_from_cache() (s3.py:1925) looks up only the string keys path and self._parent(path).
The only string-keyed listing is the bucket list under "", so for keys below a bucket the documented behavior of info() ("a cached listing of the path itself makes it a directory, and a cached listing of its parent without it means it does not exist") does not apply.

As a result, info(), size(), exists(), and du() send a HeadObject request for an object that a previous ls()/find() already listed with its size and metadata.
With list-only permissions, they fail instead of answering from the listing.

The tuple keys date from v3.15.0 (681e749).

Found by the independent review of #956 (#933).

Reproduction

fs.ls("s3://BUCKET/d")          # caches ("BUCKET/d", "/")
fs.info("s3://BUCKET/d/direct") # sends HeadObject anyway

Environment

• PyAthena master e0e85da.

Proposed fix (optional)

Let _ls_from_cache() consult the (parent, "/") listing (and the path's own (path, "/") listing for directories), or correct the info() docstring if the listing cache is intentionally not used for lookups.
Check the interaction with version_aware, which re-heads version-less cached file entries.