Numerous changes Secrets Management to address review feedback

[PaulHigin]

1. Create public SecretInformation to return for Get-SecretInfo.
2. Add vaultName to all vault extension functions.
3. Fix additionalParameters parameter in SecretManagementExtension abstract classes.
4. Add Test-Vault cmdlet, and new required extension vault TestVault() to abstract class.
5. Rename cmdlets and public types to remove 'secrets' plurality (except for Microsoft.PowerShell.SecretsManagement).
6. Change CredMan naming prefix to ps:SecretName
7. Fix return byte[] bug in example test script extension.
8. Update tests.

Note that many of these changes are breaking, and requires a complete replacement of Secrets Management module and any extension modules. Also any existing built in local vault secret can no longer be retrieved and must be re-saved.

[PaulHigin]

I am going to merge these changes before renaming the module. Renaming the module is going to be a big change, affecting CI, tests, etc., and I'll do that in a separate PR.