The TestVSphereLogin method still defaults to testing against a real vCenter,
but if the required environment variables are not set, it can test against vcsim.
More tests can be converted to use configFromEnvOrSim(), but can be in follow up PRs.
This refactor is in support of SAML token authentication: #63209
Avoid use of govmomi.Client as it only supports username+password authentication via SessionManager.Login().
Using vim25.Client directly will allow VCP to add other authentication methods,
such as SessionManager.LoginByToken().
The 'All' parameter of the 'NewFinder' function controls property collection while searching the inventory.
When 'All' is set to 'false', Finder collects the minimal set of object properties required to search inventory.
When 'All' is set to 'true', Finder collects *all* object properties, which are *not* required to search inventory.
Setting 'All' to 'true' is only useful when inspecting all properties of an object,
such as by certain govc commands when the '-json' or '-dump' flags are specified.
Changing All=false in VCP minimizes the SOAP payload size and marshalling required on both sides, without impacting any functionality.
