Add quiche code back to coverage test

[danzh2010]

Currently, the code under source/extensions/quic_listeners/quiche/ is excluded from coverage test in #7721. This is necessary because there are a lot of NOT_REACHED_GCOVR_EXCL_LINE, NOT_IMPLEMENTED_GCOVR_EXCL_LINE added in that PR which if included in coverage test would raise the bar of code coverage much higher than required (97%) for other PRs in the future. And also there are code hard to tests in non-integration tests.

When the integration is done, those macros should be replaced by real implementation or ASSERT with dummy tests. And integration tests should cover those currently hard-to-test lines. And we should add source/extensions/quic_listeners/quiche/ back to coverage test then.

[stale]

This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or other activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically closed because it has not had activity in the last 37 days. If this issue is still valid, please ping a maintainer and ask them to label it as "help wanted". Thank you for your contributions.

[danzh2010]

I almost missed this issue because it is automatically closed. Can someone re-open it?