apacheGH-38758: [C++][FS][Azure] Rename AzurePath to AzureLocation (a…

…pache#38773)

### Rationale for this change

It's for readability. `AzurePath::path_to_file` may refer a directory but its name includes `file`.

### What changes are included in this PR?

Rename `AzurePath` to `AzureLocation`:
* `AzurePath::path_to_file` -> `AzureLocation::path`
* `AzurePath::path_to_file_parts` -> `AzureLocation::path_parts`
* `AzurePath::full_path` -> `AzureLocation::all`

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* Closes: apache#38758

Authored-by: Sutou Kouhei <[email protected]>
Signed-off-by: Sutou Kouhei <[email protected]>