Fix retrieving properties by upstream ID and name

[jhrozek]

Summary

• Don't fail if lookupProperties include upstream ID but the entity does not - We recently enhanced the property service to include lookup by ID in the cache, which is great, but we didn't handle the case where the lookup properties included the upstream ID but the entity properties in the database did not. In that case we should fall back to looking the property by name.
• Don't return provifv1.ErrEntityNotFound from the property service - It was irritating to have to handle two return codes. The caller really doesn't care why was the entity not found, just that it was not found. Let's conver the provider NotFound into service Not found so that the callers have one less error to handle.

Fixes #4431

Mark the type of change your PR introduces:

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

I added a unit test. I need to do better testing, I'm just running out of time right now. I'll continue in the evening.

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[coveralls]

coverage: 53.279% (-0.03%) from 53.312%
when pulling 3d2c994 on jhrozek:prop_by_upstream_fix
into cd940ff on stacklok:main.

[jhrozek]

I did some manual testing and the patch seems to indeed help.