apacheGH-38702 [C++]: Implement AzureFileSystem::DeleteRootDirContents (

apache#39151)

### Rationale for this change

This copies the behavior implemented by S3FileSystem.

### What changes are included in this PR?

An implementation of `DeleteRootDirContent` that prevents deletion of all blob containers.

### Are these changes tested?

N/A.
* Closes: apache#38702

Authored-by: Felipe Oliveira Carvalho <felipekde@gmail.com>
Signed-off-by: Felipe Oliveira Carvalho <felipekde@gmail.com>

cpp/src/arrow/filesystem/azurefs.cc

@@ -1427,7 +1427,7 @@ Status AzureFileSystem::DeleteDirContents(const std::string& path, bool missing_
 }
 
 Status AzureFileSystem::DeleteRootDirContents() {
-  return Status::NotImplemented("The Azure FileSystem is not fully implemented");
+  return Status::NotImplemented("Cannot delete all Azure Blob Storage containers");
 }
 
 Status AzureFileSystem::DeleteFile(const std::string& path) {