Prevent deferred File.Close and wrap errors while putting CRDs into xpls provider package cache

[ulucinar]

Description of your changes

Removes the deferred File.Close call in cache.entry.writeObjects to decrease the # of simultaneously open files and wraps the error returned from cache.entry.appendToPackageJSON to provide more context.

I have:

• [x] Read and followed Upbound's contribution process.
• [x] Run make reviewable to ensure this PR is ready for review.
• [ ] Added backport release-x.y labels to auto-backport this PR, as appropriate.

How has this code been tested

Tested with Go 1.18.10 on a test configuration package with the following command:

/tmp/up xpkg dep xpkg.upbound.io/upbound/provider-gcp

(I've initially observed this issue with up@v.17.0, which uses Go 1.18)

[sttts]

🚢