pkg_files() has some odd quirks, like breaking if a filename exists in multiple directories. filegroup() does everything we need, without these quirks.
PiperOrigin-RevId: 547523447
After this change, `mini_table` only has MiniTable definitions themselves. Everything having to do with the MiniDescriptor wire format is in `mini_descriptor`.
Also rearranged some of the files in mini_table to have better structure for `internal/`.
This CL contains no functional change.
PiperOrigin-RevId: 543529112