[Feature]: Az.KeyVault Powershell module - Set-AzKeyVaultSecret cmdlet add support to hashtables in Secret Value

### Description of the new feature

The portal GUI and Azure KeyVault Extension for PowerShell Secret Management both allow hashtables in the secret value. When we attempt the same using the Az.KeyVault module we cannot use hashtables. Converting the hashtable in SecureString does not work as the end result is "System.Collections.Hashtable" when calling the Secret value as plain text.

### Proposed implementation details (optional)

_No response_