Signcheck tars

[ellahathaway]

Closes dotnet/source-build#4897

Example output

arcade-validation# ./eng/common/sdk-task.sh --task SigningValidation --restore /p:PackageBasePath=/root/repos/arcade-validation/src/Validation/Resources/*.tar.gz

Results

[File] sample.tar.gz, Skipped (unsupported file type), Signed: N/A
  [File] 5d4ced5771ae2c7fc401c0acf235f9232629c77d5025436bb311353d05759cab.nupkg, Signed: False, Virtual path: sample.tar.gz/ContainerOne.1.0.0.nupkg, Full Name: ContainerOne.1.0.0.nupkg
[File] test.tar.gz, Skipped (unsupported file type), Signed: N/A
  [File] 39329cbda43448107a41aad6930abc7f3928be3e1e377d4dfd030c0bab290b28.vsix, Skipped (unsupported file type), Signed: N/A, Virtual path: test.tar.gz/test.vsix, Full Name: test.vsix
    [File] 4593421a045154fdbe92fd48774f936c80f0c2fc1c5a978d9982d8c96a6c66c9.vsix, Skipped (unsupported file type), Signed: N/A, Virtual path: test.tar.gz/test.vsix/PackageWithRelationships.vsix, Full Name: PackageWithRelationships.vsix

Signing issues found
Total Time: 00:00:00.0850455
Total Files: 27, Signed: 0, Unsigned: 1, Skipped: 26, Excluded: 0, Skipped & Excluded: 0                         (0.2s)

This is ready, it just needs to be rebased once https://github.com/dotnet/arcade/pull/15489/files is merged.

[ellahathaway]

This PR was updating with my recent changes... closing and will reopen a new PR