Redundant metadata API calls in Azure Blob Storage operations

### Problem Description

The current `CloudPath` implementation makes multiple redundant metadata API calls during common operations like `open()`, `download_to()`, and `copy()`. Each call to `exists()`, `is_file()`, `is_dir()`, and `stat()` results in a separate `_get_metadata()` call to Azure Blob Storage, even though all these properties are available from a single metadata response.

### What happens during an `open()` call

- `open()` calls `exists()` + `is_file()`
- `_refresh_cache()` calls `stat()`
- `download_to()` calls `exists()` + `is_file()` again

On Azure, all of these end up calling the same `AzureBlobClient._get_metadata()`, which returns all the necessary information (existence, file/directory status, size, last modified time) in a single API call.

### Performance Impact

After removing the redundant calls, I was able to achieve:
* ~2× speedup for 1 MB downloads
* ~1.5× speedup for 10 MB downloads

### Proposal

There are two possible solutions:

#### Option 1: Azure-specific optimization

Optimize this in `AzureBlobClient` and `AzureBlobPath`.

**Implementation:**
- Add `_get_blob_properties()` to `AzureBlobClient` that returns all the needed information in one call
- Store the result of `AzureBlobClient._get_blob_properties()` at the start of e.g. `AzureBlobPath.open()`
- Pass metadata between internal methods to avoid redundant calls
- Alternatively implement metadata caching/invalidation logic

**Example:**
```python
def open(self, mode="r", **kwargs):
meta = self.client._get_blob_properties(self) # Single call
if meta.exists and meta.is_directory:
raise CloudPathIsADirectoryError(...)
if mode == "x" and meta.exists:
raise CloudPathFileExistsError(...)
self._refresh_cache_with_meta(meta, **kwargs) # Reuse metadata
# ... rest of implementation
```

#### Option 2: CloudPath optimization

Change `Client` API and optimize `Cloudpath`
- Modify `Client` API to explicitly require `_get_metadata()` method that will fetch all the required data
- Similar optimization to `Cloudpath` as described in option 1

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**PR for Option 1 coming**