Containers image registry implementation with opt-in caching

[joelanford]

Description of the change:
This change adds a new containers/image-based registry client and updates various (non-deprecated) commands to use it. Specifically render (and other commands that use action.Render) and alpha bundle validate. Deprecated sqlite based commands are not updated.

The intent of the PR is to keep essentially full compatibility with the containerd implementation, and to additionally gain the features of containers/image-based clients.

This PR also includes the ability to opt into caching (and reusing) downloaded blobs (when OLM_CACHE_DIR is set). The behavior around the cache is essentially --pull-policy=Always, where existing layers do not need to be redownloaded. While this PR does garbage collect unused blobs in the cache after each image pull, specifically cleaning up the cache is (for now at least) left as an exercise for the user.

Motivation for the change:
Improves alignment of opm with the ecosystem of tools it is often used with. The main benefit here is that opm calls that use this client will now honor user's existing containers/image-based configuration, including registries.conf CAs and image mappings.

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Docs updated or added to /docs
• Commit messages sensible and descriptive

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
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[codecov]

Codecov Report

Attention: Patch coverage is 53.62319% with 96 lines in your changes missing coverage. Please review.

Project coverage is 55.15%. Comparing base (2d1087f) to head (3f5bbe0).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/image/containersimageregistry/registry.go	50.79%	69 Missing and 24 partials ⚠️
internal/testutil/image/registry.go	82.35%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1626      +/-   ##
==========================================
+ Coverage   46.79%   55.15%   +8.36%     
==========================================
  Files         135      136       +1     
  Lines       15888    15911      +23     
==========================================
+ Hits         7435     8776    +1341     
+ Misses       7412     5982    -1430     
- Partials     1041     1153     +112     

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[joelanford]

This used to be in pkg/lib/image, but it is only used by tests. Given that its implicit intention is as a test utility, I think it is reasonable to move this into internal/testutil to make that intention explicit.

This is technically a breaking change, but one that I am comfortable with because a reasonable person would not expect this to actually be part of the public API surface of operator-registry.

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: grokspawn, joelanford

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• OWNERS [grokspawn,joelanford]

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[grokspawn]

/lgtm