feat: add cache entire DNS response (#833)

[0xERR0R]

Changing cache behavior:

Before this change:
Cache in caching resolver could contain either the answer slice (from positive DNS response) or the result code (as int).

After this change:
Cache contains always the entire DNS response (dns.Msg)

fixes #833

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.09 ⚠️

Comparison is base (d64b399) 93.15% compared to head (ce983ef) 93.06%.

Additional details and impacted files

@@               Coverage Diff               @@
##           development     #909      +/-   ##
===============================================
- Coverage        93.15%   93.06%   -0.09%     
===============================================
  Files               42       42              
  Lines             4950     4945       -5     
===============================================
- Hits              4611     4602       -9     
- Misses             268      271       +3     
- Partials            71       72       +1     

Impacted Files	Coverage Δ
resolver/caching_resolver.go	96.37% <100.00%> (-0.10%)	⬇️
resolver/query_logging_resolver.go	95.62% <0.00%> (-2.92%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[alpominth]

Very good work. =)

An interesting feature that would be useful to use with this is #897.

I hope you implement some day.