[FEAT] ls/list_dir for AzureBlobStorage (#1408)

File listing for AzureBlobStorage via list_blobs(prefix) API. Closes 
- #1439 

Manually checked:

- scheme:// -> all buckets
- scheme://bucket -> ls the bucket
- scheme://bucket/ -> ls the bucket
- scheme://bucket/dir -> ls the dir
- scheme://bucket/dir/ -> ls the dir
- scheme://bucket/dir// -> ls the dir
- scheme://bucket/file.txt -> returns a single File entry
- scheme://bucket/emptydir -> returns []
- scheme://bucket/MISSING should throw FileNotFoundError
- buckets and folders are returned with trailing slashes

Implementation notes:
- This reimplements iter_dir of the ObjectSource trait, since the Azure
Rust SDK exposes paginated streams directly (instead of continuation
tokens).
- Supports both protocols that fsspec supports (`az://` and `abfs://`).
Whichever protocol used is persisted.
- Supports both URI formats that fsspec supports
(`protocol://container/path-part/file` and
`protocol://[email protected]/path-part/file`), but
all results are translated to the first format.

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Co-authored-by: Xiayue Charles Lin <[email protected]>