Trigger revalidation of VCN, underlying networks

This change adds triggers additional revalidation of the VCN and
underlying networks in the following cases:

Triggers VCN Network revalidation after mobility events. This is the
most likely time that the VCN will suddenly fail to validate, this helps
to detect it as quickly as possible.

Triggers underlying network validation if the VCN validation fails; if
the underlying network fails, the VCN will migrate away. When the VCN
fails to validate, it is unclear whether it is a VCN dataplane issue, or
an underlying network issue.

Bug: 222351571
Test: atest FrameworksVcnTests
Change-Id: I4d77e9977ae7dbf0fcc1cccb29b25c57002a6daf