Order copyright immediately after the license block,
this was done almost everywhere with a few exceptions.
Remove authors from a few files (we had already removed "Contributors"
section however with old patches being applied this gets added back in).
Also move descriptive text into the doxygen comment block under \file.
In some cases remove the text as it was accidentally copied.
- Added space below non doc-string comments to make it clear
these aren't comments for the symbols directly below them.
- Use doxy sections for some headers.
- Minor improvements to doc-strings.
Ref T92709
This didn't belong on blenlib since it uses DNA data types
and included a bad-level call to BKE_curve.h.
It also meant linking in blenlib would depend on the freetype library,
noticeable for thumbnail extraction (see D6408).