Doc fixes in package.el

* lisp/emacs-lisp/package.el (package-process-define-package)
(package-generate-description-file): Doc fixes.
(package-generate-autoloads, package--write-file-no-coding)
(package--archive-file-exists-p, package-desc-status): Add doc
strings.
1 job for emacs-27 in 55 minutes and 34 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #4817
test-all

00:55:34

 
Name Stage Failure
failed
test-all Test
Makefile:319: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:294: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:959: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1