Adds tokenURL attribute for VCP service account authentication

[rvelaVenafi]

VCert SDK:

• Removes TenantID from endpoint.Authentication struct
• Cloud connector will use endpoint.Authentication.OAuthProvider.TokenURL instead of building the URL using the tenantID to obtain the access token

VCert CLI:

• Removes --tenant-id flag for getcred command
• Adds --token-url flag for getcred command

VCert Playbook:

• Removes tenantId attribute from config.connection.credentials object
• Now uses config.connection.credentials.idP.tokenURL for VCP service account authentication

[BeardedPrincess]

@rvelaVenafi: Seems we updated the codepaths for this, but not the documentation / samples. Should I open an issue, or are you already aware of this?