Async friendly Always Encrypted support

[cheenamalhotra]

Always Encrypted types today don't support async APIs in base class as well as in implementations, leading to sync-over-async in Async workflows. This gap is important to fill for a true async workflow experience when executing commands where encryption/decryption is needed to be performed.

This will be covered in following tasks:

• Introduce Async API counterparts for AE base class #3673
• Implement async counterparts in all Key Store provider implementations:
• SqlColumnEncryptionCertificateStoreProvider
• SqlColumnEncryptionCngProvider
• SqlColumnEncryptionCspProvider
• SqlColumnEncryptionAzureKeyVaultProvider
• Define virtual async counterparts in base type 'SqlColumnEncryptionEnclaveProvider'
• Implement async counterparts in all Enclave provider implementations:
• NoneAttestationEnclaveProvider
• AzureAttestationEnclaveProvider
• VirtualizationBasedSecurityEnclaveProviderBase
• Implement Async API usage in Async code paths
• Testing and code coverage