feat: copy only index file from container filesystem

[exdx]

Description of the change:
Builds off #775

Pruning an index via opm index prune can fail when permissions on the filesystem in the container are read-only. Since the command copies all files out from the container it is prone to failure. Fora example, the red hat operators catalog is based on the UBI image, which contains some directories with elevated permissions (/root/* for example). Extract the entire contents of this container filesystem via docker cp will fail. This PR copies out the content of the file by copying the container contents to stdout as a tar stream and then writing the untarred content to disk.

Motivation for the change:

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]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[codecov]

Codecov Report

Merging #800 (9fb3dec) into master (a3253eb) will decrease coverage by 1.13%.
The diff coverage is 53.29%.

❗ Current head 9fb3dec differs from pull request most recent head e9f1811. Consider uploading reports for the commit e9f1811 to get more accurate results

@@            Coverage Diff             @@
##           master     #800      +/-   ##
==========================================
- Coverage   50.90%   49.77%   -1.14%     
==========================================
  Files         102      108       +6     
  Lines        8753     9342     +589     
==========================================
+ Hits         4456     4650     +194     
- Misses       3458     3807     +349     
- Partials      839      885      +46     

Impacted Files	Coverage Δ
pkg/containertools/runner.go	0.00% <0.00%> (ø)
pkg/lib/bundle/exporter.go	56.66% <0.00%> (ø)
pkg/lib/bundle/supported_resources.go	100.00% <ø> (ø)
pkg/lib/bundle/validate.go	60.69% <0.00%> (ø)
pkg/lib/indexer/indexer.go	10.67% <0.00%> (-0.11%)	⬇️
pkg/registry/parse.go	73.68% <ø> (ø)
pkg/sqlite/query.go	64.53% <0.00%> (-0.08%)	⬇️
alpha/declcfg/diff_include.go	28.30% <2.66%> (-62.33%)	⬇️
pkg/image/containerdregistry/registry.go	4.38% <45.45%> (ø)
pkg/lib/registry/registry.go	19.50% <48.00%> (-4.11%)	⬇️
... and 15 more

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[exdx]

Seeing a new interesting failure

 • Failure [33.719 seconds]
opm
/home/runner/work/operator-registry/operator-registry/test/e2e/opm_test.go:219
  using docker
  /home/runner/work/operator-registry/operator-registry/test/e2e/opm_test.go:489
    builds and manipulates bundle and index images [It]
    /home/runner/work/operator-registry/operator-registry/test/e2e/opm_test.go:260

    Unexpected error:
        <sqlite3.Error>: {
            Code: 1,
            ExtendedCode: 1,
            err: "no such table: operatorbundle",
        }
        no such table: operatorbundle
    occurred

    /home/runner/work/operator-registry/operator-registry/test/e2e/opm_test.go:318

[openshift-ci]

@exdx: PR needs rebase.

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