Create and document auth-source-reveal-mode

* lisp/auth-source.el (auth-source-reveal-mode): Add new minor
mode to hide passwords. Remove authinfo-mode which provided a
major mode for the same purpose before. Use the text-coverup API.

* doc/misc/auth.texi (Hiding passwords in text buffers): Document
auth-source-reveal-mode.
2 jobs for scratch/tzz/prettify-text-mode in 40 minutes and 25 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Test
failed #6619
test-all

00:00:12

passed #6620
test-filenotify-gio

00:40:24

 
Name Stage Failure
failed
test-all Test
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fatal: failed to run reflog
ERROR: Job failed: exit code 1