docs: clean up field usage

We currently have a mixture of several fields in our package docs. Between historic patterns and new workflows, each package may feature one or more of:

1. comment - a generic field for providing commentary on a package. This was previously always used to provide a link to a GPL sources tarball if required for a package
2. warning - usually used to indicate we've had to skip some sort of test or omit a piece of functionality in a module, due to incompatibility or known issues with riscv64 or our infrastructure
3. patched - a typically blank field used to signal that the package is built with one or more patches applied during the process

These are all somewhat redundant. I propose two to replace these:

1. gpl-sources - specify this with one or more links if we have to provide GPL source tarballs as part of the package builds
2. comment - anything else (notes about patching, skipping tests, etc.) goes here

@justeph @luhenry thoughts?

The issue does not name specific files or tests; first locate the package documentation fields that currently use comment, warning, and patched. Confirm the proposed field scheme before migrating entries: use gpl-sources for GPL source links and comment for other notes, then verify no old field usage remains.