Added new env var PARENT_PIPELINE_MERGE_REQUEST_REF_PATH to e2e:perf-on-cng job

What does this MR do and why?

This change adds a new environment variable to the performance testing configuration. The new variable captures information about merge request references, which will allow the performance tests to better track and identify which specific merge request triggered the test run. This is a small enhancement to improve test tracking and debugging capabilities.

Also changed the rule to prevent the job from running on tier 1 only. This lines up with e2e:test-on-cng job.

References

gitlab-org/quality/component-performance-testing#108

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