Add VAPI bindings for guest namespaces and virtual machine classes

[spacegospod]

Description

We already have bindings for supervisor enable/disable.
I am building on top of those to add support for guest namespace and virtual machine class CRUD operations.

I have taken into account the fact that the original supervisor bindings were implemented when vSphere 7.0.3 was the latest version in existence and I have made sure that these new bindings do not use anything that was added to the API after 7.0.3.

For reference:
https://developer.vmware.com/apis/vsphere-automation/v7.0U3/vcenter/api/vcenter/namespaces/instances/
https://developer.vmware.com/apis/vsphere-automation/v7.0U3/vcenter/namespace_management/

Type of change

Please mark options that are relevant:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to
  not work as expected)
• This change requires a documentation update
• Build related change

How Has This Been Tested?

I ran the "lint-fix" and "test" make scripts
I also added new cases to "namespace.bats"
And of course I implemented & tested the whole thing with a live vCenter. These changes work with 7.0.3 and with 8.0.X

Checklist:

• My code follows the CONTRIBUTION guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged

[dougm]

Thanks @stoyanzhelyazkov , looks good overall. Mainly changing the handful of commands to use ARG instead of -flag would be good to make in this PR before merging.

[dougm]

Thanks @stoyanzhelyazkov !