* backport of commit 008451aa1e
* backport of commit abdf8c8205
* backport of commit a0176356f7
* DNS v2 - split up router into multiple responsibilities & break up router tests into multiple files. (#20688)
* Update agent/dns.go
Co-authored-by: Michael Zalimeni <michael.zalimeni@hashicorp.com>
* PR feedback
* split tests out into multiple files.
* Extract responsibilities from router into discoveryResultsFetcher, messageSerializer, responseGenerator.
* adding recordmaker tests
* add response generator test coverage.
* changing tests case name based on PR feedback
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Co-authored-by: Michael Zalimeni <michael.zalimeni@hashicorp.com>
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Co-authored-by: John Murret <john.murret@hashicorp.com>
Co-authored-by: Michael Zalimeni <michael.zalimeni@hashicorp.com>