Fix link cycle detection

[wagoodman]

PR #154 added a regression where link resolution may result in falsely claiming that there is a link cycle for links that reference the same path twice while resolving links for a single path.

For example:

# links:
   /usr/local/bin/ksh -> /bin/ksh
   /bin -> /usr/bin
   /etc/alternatives/ksh -> /bin/ksh93

# real file: 
   /usr/bin/ksh93

In this case while resolving links in the /usr/local/bin/ksh path, the /usr/bin path is resolved twice, which under the current (buggy) implementation will falsely claim that there is a cycle relating to /usr/bin.

Relates to anchore/syft#1586

[github-actions]

Benchmark Test Results

Benchmark results from the latest changes vs base branch

latest: Pulling from library/ubuntu
goos: linux
goarch: amd64
pkg: github.com/anchore/stereoscope/pkg/file
cpu: Intel(R) Xeon(R) Platinum 8272CL CPU @ 2.60GHz
docker: 
           │ ./.tmp/benchmark-5bbb589.txt │
           │            sec/op            │
TarIndex-2                   41.94µ ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

           │ ./.tmp/benchmark-5bbb589.txt │
           │             B/op             │
TarIndex-2                  5.560Ki ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

           │ ./.tmp/benchmark-5bbb589.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-5bbb589.txt │
                                      │            sec/op            │
SimpleImage_GetImage/docker-archive-2                   1.522m ± ∞ ¹
SimpleImage_GetImage/oci-archive-2                      1.222m ± ∞ ¹
SimpleImage_GetImage/oci-dir-2                          805.5µ ± ∞ ¹
geomean                                                 1.144m
¹ need >= 6 samples for confidence interval at level 0.95

                                      │ ./.tmp/benchmark-5bbb589.txt │
                                      │             B/op             │
SimpleImage_GetImage/docker-archive-2                  354.0Ki ± ∞ ¹
SimpleImage_GetImage/oci-archive-2                     632.6Ki ± ∞ ¹
SimpleImage_GetImage/oci-dir-2                         399.8Ki ± ∞ ¹
geomean                                                447.4Ki
¹ need >= 6 samples for confidence interval at level 0.95

                                      │ ./.tmp/benchmark-5bbb589.txt │
                                      │          allocs/op           │
SimpleImage_GetImage/docker-archive-2                   2.732k ± ∞ ¹
SimpleImage_GetImage/oci-archive-2                      1.550k ± ∞ ¹
SimpleImage_GetImage/oci-dir-2                          1.334k ± ∞ ¹
geomean                                                 1.781k
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-5bbb589.txt │
                                                   │            sec/op            │
SimpleImage_FetchSquashedContents/docker-archive-2                   17.13µ ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

                                                   │ ./.tmp/benchmark-5bbb589.txt │
                                                   │             B/op             │
SimpleImage_FetchSquashedContents/docker-archive-2                  2.648Ki ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

                                                   │ ./.tmp/benchmark-5bbb589.txt │
                                                   │          allocs/op           │
SimpleImage_FetchSquashedContents/docker-archive-2                    21.00 ± ∞ ¹
¹ need >= 6 samples for confidence interval at level 0.95

[kzantow]

👍