[release-1.22] Fully remove public internet dependency on DNS tests

[istio-testing]

Manual cherrypick required.

#1075 failed to apply on top of branch "release-1.22":

Applying: Fully remove public internet dependency on DNS tests
Using index info to reconstruct a base tree...
M	src/telemetry.rs
Falling back to patching base and 3-way merge...
Auto-merging src/telemetry.rs
CONFLICT (content): Merge conflict in src/telemetry.rs
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Fully remove public internet dependency on DNS tests
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

[howardjohn]

blocked by #1073

[zirain]

approved #1073

[howardjohn]

Oops, the blocker was approved not the cherrypick