WIP: DiscoveryEngineDataStoreTargetSite controller & tests

[justinsb]

• DiscoveryEngineTargetSite: initial types
• DiscoveryEngineTargetSite: generated apimachinery
• DiscoveryEngineDataStoreTargetSite: create test
• tests: golden output
• Fixes to API (should go into previous PR)
• Autogen fixes (should go into previous PR)
• tests: normalization for DiscoveryEngineDataStoreTargetSite
• DiscoveryStoreDataStoreTargetSite: controller
• chore: create shared project number/id mapper
• DiscoveryEngineDataStoreTargetSite: mockgcp support

[google-oss-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please ask for approval from justinsb. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment