Add insecure flag to push and pull

[erbesharat]

What this PR does / why we need it:
Adds the ability to push and pull from insecure registries to the crane cmd.
The flag also had to be added to a few other subcommands like export, append and etc.

Which issue this PR fixes:
fixes #633

Special notes for your reviewer:
I wasn't sure if it's ok to change the handler map in the validate subcommand without any prior discussions, so I just added the options argument to makeTarball as a temporary fix so we don't have failing tests.
Let me know if it's ok to change the handler map and also what do you think is a good approach to change it.
https://github.com/google/go-containerregistry/pull/634/files#diff-67c9d71faf9a3b5faa49b6f666170f54R72

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[codecov-io]

Codecov Report

Merging #634 into master will increase coverage by 0.24%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #634      +/-   ##
==========================================
+ Coverage   76.29%   76.53%   +0.24%     
==========================================
  Files         101      101              
  Lines        4412     4483      +71     
==========================================
+ Hits         3366     3431      +65     
  Misses        636      636              
- Partials      410      416       +6

Impacted Files	Coverage Δ
pkg/crane/pull.go	87.5% <100%> (ø)	⬆️
pkg/crane/push.go	100% <100%> (ø)	⬆️
pkg/v1/remote/catalog.go	67.64% <0%> (-0.36%)	⬇️
pkg/internal/retry/retry.go	100% <0%> (ø)	⬆️
pkg/internal/compare/index.go	76.47% <0%> (+5.88%)	⬆️
pkg/v1/remote/list.go	76.66% <0%> (+11.44%)	⬆️
pkg/internal/compare/image.go	76.47% <0%> (+11.76%)	⬆️
pkg/crane/catalog.go	100% <0%> (+37.5%)	⬆️

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[imjasonh]

Thanks for this change! Small comment otherwise looks good.

[jonjohnsonjr]

You'll want to run ./hack/update-code-gen.sh to re-generate the docs, otherwise lgtm.

I wasn't sure if it's ok to change the handler map in the validate subcommand without any prior discussions, so I just added the options argument to makeTarball as a temporary fix so we don't have failing tests.

I don't see any problem with what you've done here, that looks like what I'd have done.

addressed