direct: Exclude deploy-only fields from Apps update mask

[simonfaltum]

Why

When an Apps resource changes both description and lifecycle.started in the same deploy, the direct engine produces an update_mask of "description,lifecycle". The Apps Update API rejects it:

Error: cannot update resources.apps.myapp: updating id=...: Invalid update mask.
Only description, budget_policy_id, usage_policy_id, resources, user_api_scopes,
compute_size, compute_min_instances, compute_max_instances, git_repository,
telemetry_export_destinations are allowed.
Supplied update mask: description, lifecycle
(400 INVALID_PARAMETER_VALUE)

lifecycle is a deploy-only field managed by the CLI (via start/stop + the Deployments API), not by the App Update endpoint.

This surfaced in the nightly run lifecycle-started/DATABRICKS_BUNDLE_ENGINE=direct acceptance test. Locally the mock server does not validate the update mask, so the bug slipped through.

Changes

Before: DoUpdate collected every Update path in the plan entry, truncated each to its top-level field, and joined them into the mask. Deploy-only fields (source_code_path, config, git_source, lifecycle) leaked into the mask whenever they changed alongside a real App field.

Now: filter deployOnlyFields out of the collected paths before building the mask. The hasAppChanges gate already applies the same filter to decide whether to call Update at all; this matches the mask to the same set of fields.

Also updated lifecycle-started acceptance test to print //apps instead of only //deployments for the two steps that toggle started and change description together, so the update_mask now appears in the recorded output. Without the fix the mask shows "description,lifecycle"; with the fix it shows "description" only.

Test plan

• go test ./bundle/direct/... passes
• go test ./acceptance -run 'TestAccept/bundle/resources/apps/' passes (all engines)
• make checks passes
• Nightly lifecycle-started/direct + related tests pass on cloud