fix(dns): bug with standard lookup tags not working; SRV questions returning duplicate hostnames

[DanStough]

This closes:

• v2dns makes SRV records unusable #21325
• consul 1.19.0 breaks all tags #21336

Description

Two bugs with the V2 DNS implementation were discovered:

• For SRV requests, we would return node hostnames for service instances even though they were all the same and the service instances have unique IPs. v2dns makes SRV records unusable #21325
• We weren't parsing tags for standard lookups. consul 1.19.0 breaks all tags #21336
  • We also weren't returning any errors if there were too many query parts. It's possible people were using periods in tag names, but I think we still want to remove that behavior, so it should error.

Testing & Reproduction steps

Unit tests now fully cover these cases. We were missing coverage for these particular uses:

• We were testing RFC 2782 style lookups with tags, not standard lookups. We were also not registering multiple instances to check if tag filtering was working.
• RE: SRV using hostnames instead of encoded IPs. There is something different about using the API vs. internal RPCs to register services. I looked at how Nomad does this to replicate the specific

[boruszak]

Release notes changes LGTM!

Approving on behalf of consul-docs