Support enforceInTransit field in PubSubTopic MessageStoragePolicy

[codebot-robot]

This PR adds support for the enforceInTransit parameter under messageStoragePolicy in the PubSubTopic CRD (pubsubtopics.pubsub.cnrm.cloud.google.com).

Changes

• Updated the local/vendored TPG Beta provider (resource_pubsub_topic.go) to add enforce_in_transit to the message_storage_policy schema, including its expander/flattener mapping helpers.
• Added the EnforceInTransit *bool field under the MessageStoragePolicy struct in apis/pubsub/v1beta1/topic_types.go.
• Added mapping logic for EnforceInTransit to pkg/controller/direct/pubsub/topic_mapper.go.
• Promoted .message_storage_policy.enforce_in_transit to a SpecField in pkg/controller/direct/pubsub/topic_fuzzer.go.
• Regenerated manifests (CRDs, DeepCopy functions, generated clients).
• Updated the E2E golden tests for pubsubtopic to configure enforceInTransit: true during creation and enforceInTransit: false during update to verify correct handling in both states.

Fixes #9649

[google-oss-prow]

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[justinsb]

@maqiuyujoyce I think this works - adding to both controllers (I've just reassigned back to codebot-robot to regenerate the clients, I'm assuming). Mind taking a look with me (I did cross-check against the terraform code, but I'm not sure I'm much more competent than the AI here 😂 )

[justinsb]

We have a unit test failure:

=== NAME  TestSpecAndStatusToYAML
    utils.go:150: FAIL: unexpected diff in testdata/pubsubtopic-spec.yaml.golden:   (
          	"""
          	... // 6 identical lines
          	  allowedPersistenceRegions:
          	  - string
        + 	  enforceInTransit: boolean
          	resourceID: string
          	schemaSettings:
          	... // 6 identical lines
          	"""
          )
--- FAIL: TestSpecAndStatusToYAML (7.78s)