feat: gator test --deny-only flag

[WnP]

What this PR does / why we need it:

Add --deny-only flag to gator test command.

Which issue(s) this PR fixes:
Fixes #3808

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 84.21053% with 3 lines in your changes missing coverage. Please review.

Project coverage is 47.83%. Comparing base (3350319) to head (3304001).
Report is 249 commits behind head on master.

Files with missing lines	Patch %	Lines
cmd/gator/test/test.go	84.21%	2 Missing and 1 partial ⚠️

❗ There is a different number of reports uploaded between BASE (3350319) and HEAD (3304001). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (3350319)	HEAD (3304001)
unittests	2	1

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3809      +/-   ##
==========================================
- Coverage   54.49%   47.83%   -6.67%     
==========================================
  Files         134      235     +101     
  Lines       12329    19876    +7547     
==========================================
+ Hits         6719     9507    +2788     
- Misses       5116     9479    +4363     
- Partials      494      890     +396     

Flag	Coverage Δ
unittests	47.83% <84.21%> (-6.67%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[JaydipGabani]

lgtm, Thanks for the pr!