Upgrade frameworks version of golangci-lint

[willbeason]

Use the same linters we use in gatekeeper/ for consistency.

Remove usage of deprecated/now-unsupported linters.

Make changes to make linting pass.

Signed-off-by: Will Beason willbeason@google.com

[codecov-commenter]

Codecov Report

Merging #139 (10ca257) into master (2924b2c) will increase coverage by 0.13%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #139      +/-   ##
==========================================
+ Coverage   42.39%   42.52%   +0.13%     
==========================================
  Files          49       49              
  Lines        2951     2958       +7     
==========================================
+ Hits         1251     1258       +7     
+ Misses       1321     1320       -1     
- Partials      379      380       +1     

Flag	Coverage Δ
unittests	42.52% <ø> (+0.13%)	⬆️

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

Impacted Files	Coverage Δ
...eworks/constraint/pkg/regorewriter/regorewriter.go	54.32% <0.00%> (-0.40%)	⬇️
...-agent/frameworks/constraint/pkg/client/backend.go	68.75% <0.00%> (ø)
...t/frameworks/constraint/pkg/client/rego_helpers.go	82.60% <0.00%> (ø)
.../frameworks/constraint/pkg/regorewriter/sources.go	17.07% <0.00%> (ø)
...frameworks/constraint/pkg/apis/templates/scheme.go	20.00% <0.00%> (ø)
...frameworks/constraint/pkg/regorewriter/filepath.go	100.00% <0.00%> (ø)
...meworks/constraint/pkg/regorewriter/ast_helpers.go	55.55% <0.00%> (ø)
...eworks/constraint/pkg/apis/templates/crd_schema.go	50.00% <0.00%> (ø)
...works/constraint/pkg/apis/templates/v1/register.go	0.00% <0.00%> (ø)
...rks/constraint/pkg/apis/templates/v1/conversion.go	80.00% <0.00%> (ø)
... and 8 more

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[maxsmythe]

LGTM with nits

[sozercan]

Thank you! LGTM pending @maxsmythe's comments

[sozercan]

@willbeason good to merge?