fix: don't apply basepath when looking up image names for re-tagging multi-arch images

[dsiebel]

Fixes: #8380

Description

Addresses the issue described in #8380 where re-tagging multi-arch builds with e.g. a cache tag, re-tags the first manifest returned by the registry instead of re-tagging the multi-arch manifest.

Further details are described in this issue comment.

User facing changes (remove if N/A)

Before: running skaffold build --tag xy for an already existing multi-arch image would re-tag e.g. the *_amd64 image version instead of the multi-arch manifest (no suffix).
This results in errors when trying to pull the xy image tag on a non-matching arch, e.g. arm64.

After: running skaffold build --tag xy for an already existing multi-arch image adds a tag xy to the multi-arch manifest.

[conventional-commit-lint-gcf]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
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[gsquared94]

thanks @dsiebel for opening this. I submitted #8493 with a fix that addresses all scenarios including this one for incorrect platform selected during retagging.