[chore] lint fixes

[shaneutt]

What this PR does / why we need it:

Enables lint checks on the hack/ and internal/ directories and cleans up all found linter issues.

Also the gci linter is disabled because it's problematic, but a target for running goimports is added which will help keep the imports consistent.

Which issue this PR fixes

Fixes #1597

[rainest]

#1589 introduced conflicts, whoops.

Do we in fact want to include hack/? That seems like it should be skipped for the most part since it's mostly not-Go aside from the templates, and the templates we should catch issues in the generated code without the template markup (including internal/ means we do check the output). Apparently it doesn't complain about anything currently, but it still seems wrong.

While we're here, it looks like we can strip pkg/client (it no longer exists). Do we want to include pkg/clientset?

[shaneutt]

#1589 introduced conflicts, whoops.

I fixed in 1decdda

Do we in fact want to include hack/? That seems like it should be skipped for the most part since it's mostly not-Go aside from the templates, and the templates we should catch issues in the generated code without the template markup (including internal/ means we do check the output). Apparently it doesn't complain about anything currently, but it still seems wrong.

Anywhere there is go code, we should lint it

While we're here, it looks like we can strip pkg/client (it no longer exists). Do we want to include pkg/clientset?

Sounds good 9f9cf7f

[codecov]

Codecov Report

Merging #1599 (e972a14) into next (10c0b42) will decrease coverage by 0.04%.
The diff coverage is 24.24%.

@@            Coverage Diff             @@
##             next    #1599      +/-   ##
==========================================
- Coverage   46.19%   46.15%   -0.05%     
==========================================
  Files          71       71              
  Lines        6736     6745       +9     
==========================================
+ Hits         3112     3113       +1     
- Misses       3256     3261       +5     
- Partials      368      371       +3     

Flag	Coverage Δ
integration-test	46.15% <24.24%> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
internal/cmd/rootcmd/rootcmd.go	28.57% <ø> (ø)
...trollers/configuration/zz_generated_controllers.go	32.59% <ø> (ø)
internal/ctrlutils/utils.go	93.75% <ø> (-2.09%)	⬇️
internal/deckgen/generate.go	50.61% <ø> (ø)
internal/diagnostics/server.go	64.00% <0.00%> (-3.57%)	⬇️
internal/kongstate/kongstate.go	37.55% <0.00%> (ø)
internal/kongstate/types.go	75.00% <0.00%> (-8.34%)	⬇️
internal/parser/ingressrules.go	66.66% <ø> (+7.14%)	⬆️
internal/proxy/clientgo_cached_proxy_resolver.go	60.26% <0.00%> (ø)
internal/sendconfig/sendconfig.go	53.78% <ø> (ø)
... and 23 more

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