apple_dns: Add DNS query trace

[fredyw]

This PR adds trace info in the DNS resolution details by setting the envoy.enable_dfp_dns_trace runtime flag to true. This can be useful for debugging issues, such as debugging resolve timeout issues.

Risk Level: low (only enabled with enable_dfp_dns_trace runtime flag) Testing: unit tests Docs Changes: n/a Release Notes: n/a Platform Specific Features: dynamic forward proxy, apple dns

[repokitteh-read-only[bot]]

As a reminder, PRs marked as draft will not be automatically assigned reviewers, or be handled by maintainer-oncall triage.

Please mark your PR as ready when you want it to be reviewed!

:cat:

Caused by: https://github.com/envoyproxy/envoy/pull/36678 was opened by fredyw.

see: more, trace.

[fredyw]

/assign @alyssawilk

[fredyw]

/retest

[fredyw]

/retest