feat(rst): add microsoft azure blob support

[swartzn]

What does this PR do / why do we need it?

Required for all PRs.

I got a little carried away one day and these changes just seemed to work. When I found LocalStack which is an AWS emulator, I was curious about Azure and found Azurite. Since Azure is not S3-compliant so this required a couple modifications to protobuf.

• Implements RST provider for Azure blobs with the exception of multi-part upload/download

Note: Requires protobuf branch swartzn/add-azure-support

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What are the next steps after this PR?

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[swartzn]

@swartzn Squash commits before merging if needed

To fix the issue, change the assignment on line 374 from direct assignment to the outer err variable (of type error interface) to a short variable declaration, capturing the returned error value as its concrete type. This allows the subsequent nil check (if err != nil) to work as intended. Only assign to the outer return variable err after the check and if necessary (as in the error-handling block).

• Specifically, replace:

  if lockedInfo, writeLockSet, _, err = GetLockedInfo(...); err != nil {
  

  with:

  var getLockedErr error
  if lockedInfo, writeLockSet, _, getLockedErr := GetLockedInfo(...); getLockedErr != nil {
      err = fmt.Errorf(..., getLockedErr.Error())
      return
  }
  

This avoids the interface nil problem entirely.

Only the region inside common/rst/blob.go at line 374 requires changing, introducing a new error variable for this block-scoped assignment.

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