Add Network Management ConnectivityTest resource

[modular-magician]

Release Note Template for Downstream PRs (will be copied)

`google_network_management_connectivity_test`

Also:

• Added a new override to MMv1 for the name of the resource in the filename only .
  • Prevent resource file from ending in "test" and treated as a Go test (_test.go pattern) while still keeping the name of the resource short

Derived from GoogleCloudPlatform/magic-modules#3601

[ghost]

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