[Feature]: Support the parameter DestBlobType on Start-AzStorageBlobCopy

### Description of the new feature

Currently Copy-AzStorageBlob has the parameter DestBlobType which enables the conversion of page blobs to block blobs and vice versa.

Due to a bug in Copy-AzStorageBlob (#25105) it is currently only possible to migrate between page and block blobs synchronously. While -AsJob will be fixed, it would be nice if there was feature parity between these 2 cmdlets.

The parameter is useful when converting VM disks into block blobs. We use this to archive old VMs in a cost effective way by storing them in archival storage. As page blobs can't be archived we must first convert them to block blobs.

### Proposed implementation details (optional)

Implement it the same way that Copy-AzStorageBlob does it (if possible)

Start by comparing Start-AzStorageBlobCopy with Copy-AzStorageBlob, focusing on how DestBlobType is declared and handled. Check the existing asynchronous -AsJob path and the related Copy-AzStorageBlob issue, then verify that page-to-block and block-to-page conversions work through Start-AzStorageBlobCopy as well.

Written by the indexing model from the issue text.