DRAFT: Improve architecture selection

[willmurphyscode]

This is a draft PR to track improving architecture selection in stereoscope.

Basically, when a user of syft or grype specifies a digest, we should not validate the platform, since a digest is an unambiguous reference, but we fail on the platofrm. For example:

❯ grype mcr.microsoft.com/cbl-mariner/base/core:2.0.20220731-amd64@sha256:3c0f7e103ff3c39e81e7c9c042d2b321d833fb6d26d8636567f7d88a6bdde74a
 ✔ Vulnerability DB        [no update available]
 ⠹ Pulling image           2 Layers▕ █▏[28 MB] Extracting...
1 error occurred:
	* failed to catalog: could not fetch image "mcr.microsoft.com/cbl-mariner/base/core:2.0.20220731-amd64@sha256:3c0f7e103ff3c39e81e7c9c042d2b321d833fb6d26d8636567f7d88a6bdde74a": unable to use DockerDaemon source: image has unexpected architecture "amd64", which differs from the user specified architecture "arm64"

This was probably introduced by #152 in fixing #149.

The goal of this change is to preserve the fix to #149 but remove the issue, seen via grype above, where unambiguous requests fail at

stereoscope/pkg/image/docker/daemon_provider.go

Line 348 in e14bc44

return fmt.Errorf("image has unexpected architecture %q, which differs from the user specified architecture %q", i.Architecture, p.platform.Architecture)

even when the user didn't pass --platform.

It's a draft pull request for now because I need to make test images at https://github.com/anchore/test-images to exercise the different scenarios in stereoscope integration tests before it can be merged.

[github-actions]

Benchmark Test Results

Benchmark results from the latest changes vs base branch

latest: Pulling from library/ubuntu
dbf6a9befcde: Pull complete
tar: Option --mtime: Treating date 'UTC 2019-09-16' as 2019-09-16 00:00:00
goos: linux
goarch: amd64
pkg: github.com/anchore/stereoscope/pkg/file
cpu: Intel(R) Xeon(R) Platinum 8272CL CPU @ 2.60GHz
docker: 
           │ ./.tmp/benchmark-2315cea.txt │
           │            sec/op            │
TarIndex-2                   42.52µ ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

           │ ./.tmp/benchmark-2315cea.txt │
           │             B/op             │
TarIndex-2                  5.560Ki ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

           │ ./.tmp/benchmark-2315cea.txt │
           │          allocs/op           │
TarIndex-2                    93.00 ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

pkg: github.com/anchore/stereoscope/test/integration
                                      │ ./.tmp/benchmark-2315cea.txt │
                                      │            sec/op            │
SimpleImage_GetImage/docker-archive-2                   1.553m ± ∞ ¹
SimpleImage_GetImage/oci-archive-2                      1.297m ± ∞ ¹
SimpleImage_GetImage/oci-dir-2                          805.5µ ± ∞ ¹
geomean                                                 1.175m
¹ need >= 6 samples for confidence interval at level 0.95

                                      │ ./.tmp/benchmark-2315cea.txt │
                                      │             B/op             │
SimpleImage_GetImage/docker-archive-2                  363.6Ki ± ∞ ¹
SimpleImage_GetImage/oci-archive-2                     646.1Ki ± ∞ ¹
SimpleImage_GetImage/oci-dir-2                         413.4Ki ± ∞ ¹
geomean                                                459.7Ki
¹ need >= 6 samples for confidence interval at level 0.95

                                      │ ./.tmp/benchmark-2315cea.txt │
                                      │          allocs/op           │
SimpleImage_GetImage/docker-archive-2                   2.842k ± ∞ ¹
SimpleImage_GetImage/oci-archive-2                      1.564k ± ∞ ¹
SimpleImage_GetImage/oci-dir-2                          1.348k ± ∞ ¹
geomean                                                 1.816k
¹ need >= 6 samples for confidence interval at level 0.95

docker: Error response from daemon: Get "http://localhost/v2/": dial tcp [::1]:80: connect: connection refused.
                                                   │ ./.tmp/benchmark-2315cea.txt │
                                                   │            sec/op            │
SimpleImage_FetchSquashedContents/docker-archive-2                   17.46µ ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

                                                   │ ./.tmp/benchmark-2315cea.txt │
                                                   │             B/op             │
SimpleImage_FetchSquashedContents/docker-archive-2                  2.648Ki ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

                                                   │ ./.tmp/benchmark-2315cea.txt │
                                                   │          allocs/op           │
SimpleImage_FetchSquashedContents/docker-archive-2                    21.00 ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

[wagoodman]

@willmurphyscode is this PR still needed?