AIP-10027 : Cleaning up resource retry strategy feature

[v-abhijeets]

Summary

Removes the resourceRetryStrategy / DoWithResourceAwareRetry path added
in AIP-9672. Quota-aware flow control is now fully handled by the JetStream
BackpressureWaiter (AIP-9985, PR #13), so the per-trigger retry mechanism
is redundant.

Jira: AIP-10027
Supersedes: AIP-9672

Changes

Removed

• common/retry.go: IsResourceConstraintError, DoWithResourceAwareRetry
• common/retry_test.go: tests for the above
• pkg/apis/sensor/v1alpha1/types.go: Trigger.ResourceRetryStrategy field
• pkg/apis/sensor/v1alpha1/zz_generated.deepcopy.go: corresponding deepcopy
• sensors/listener.go: switched actionFunc from
  DoWithResourceAwareRetry back to DoWithRetry

Unchanged

• DoWithRetry remains the single trigger-retry helper
• Backpressure path (BackpressureWaiter, HasCapacity,
  WaitForCapacity, getBackpressureConfig, setupBackpressure, and the
  RESOURCE_QUOTA_NAME / BACKPRESSURE_* env-var wiring)

Net diff: +1 / -164 across 5 files.

Compatibility

• resourceRetryStrategy was never published in CRD / OpenAPI / proto /
  jsonschema / examples, so no external schema or kubectl apply
  behaviour changes. No codegen regeneration needed.
• Existing Sensor CRs with resourceRetryStrategy set continue to apply;
  the field is silently ignored.
• Quota errors are now retried under the normal retryStrategy (same as
  any other error). On JetStream sensors with backpressure env vars set,
  this is a no-op since backpressure prevents the trigger from running
  when quota is full.

Testing

• go build ./... and make test pass locally.
• Removed only the tests that referenced deleted symbols; all other retry
  and backpressure tests are unchanged.
• Verified no remaining references in the repo via
  rg 'resourceRetryStrategy|DoWithResourceAwareRetry|IsResourceConstraintError'.