cds: set config_reload and config_reload_time_ms

[dkumazawa]

Commit Message: Records config_reload and config_reload_time_ms statistics when cds makes a non-empty update.
Additional Description: N/A
Risk Level: Low
Testing: Unit tests have been updated to validate that the new stats are properly set.
Docs Changes: N/A
Release Notes: N/A
Platform Specific Features: N/A

#38490

[repokitteh-read-only]

Hi @dkumazawa, welcome and thank you for your contribution.

We will try to review your Pull Request as quickly as possible.

In the meantime, please take a look at the contribution guidelines if you have not done so already.

🐱

Caused by: #38638 was opened by dkumazawa.

see: more, trace.

[dkumazawa]

There's one error from //test/extensions/filters/http/wasm:wasm_filter_integration_test in tsan. I'm wondering if this is just a flake given the previous invocation was successful.

[dkumazawa]

/retest

[zuercher]

Looks good to me. Thanks!

[dkumazawa]

Thank you @zuercher for your review! @yanavlasov please let me know if you could help provide maintainer review workflow approval or if I should reach out elsewhere (apologies for the noob question as this is my first PR to Envoy!)