feat: use builtin ORAS cache for skeleton packages

[AustinAbro321]

Description

In #3767 we created a generic cache for ORAS layers. This is used by default, but we also have a special implementation of caching specifically for skeleton packages. This PR removes that implementation so only the generic cache is used. By doing this we get closer to enabling the ability for users to turn off the cache.

Checklist before merging

• Test, docs, adr added or updated as needed
• Contributor Guide Steps followed

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[codecov]

Codecov Report

❌ Patch coverage is 10.00000% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/pkg/packager/load/import.go	10.00%	9 Missing ⚠️

Files with missing lines	Coverage Δ
src/pkg/packager/load/import.go	51.30% <10.00%> (+0.13%)	⬆️

... and 1 file with indirect coverage changes

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