Add GRPC route mirror test

[fabian4]

What type of PR is this?

/kind test

What this PR does / why we need it:

Adds GRPCRoute mirror test. Increase conformance feature coverage of GRPCRoute

Which issue(s) this PR fixes:

Fixes #3514

Does this PR introduce a user-facing change?:

NONE

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: fabian4 / name: Fabian Bao (a5ed4fe, d821b9c, 798b491)

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[k8s-ci-robot]

Hi @fabian4. Thanks for your PR.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: fabian4
Once this PR has been reviewed and has the lgtm label, please assign shaneutt for approval. For more information see the Code Review Process.

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[LiorLieberman]

/ok-to-test

[LiorLieberman]

Thanks!

[LiorLieberman]

Thanks! Can you fix the lint issues?

Also, have you checked the tests are running successfully?

[fabian4]

/retest