Use only one function to retrieve/set lossage size

* src/keyboard.c (update-lossage-size):
Rename it as lossage-size.
Called with no arguments, return the current lossage limit.
Called with ARG sets the lossage limit.
All callers updated.

* doc/emacs/help.texi: Ammend documentation.
* etc/NEWS: Amend entry.
* lisp/help.el (view-lossage): Fix docstring.

* lisp/comint.el (comint-send-invisible)
* lisp/term.el (term-read-noecho):
Mention the new command in the docstrings.

* test/src/keyboard-tests.el: Ammend test.
2 jobs for bug#38796-lossage-limit in 85 minutes and 25 seconds (queued for 5 seconds)
latest
Status Job ID Name Coverage
  Test
failed #7343
test-all

01:25:25

failed #7344
test-filenotify-gio

00:35:25

 
Name Stage Failure
failed
test-all Test
  ELC      lisp/eshell/eshell-tests.elc
GEN lisp/eshell/eshell-tests.log
ELC lisp/faces-tests.elc
GEN lisp/faces-tests.log
ELC lisp/ffap-tests.elc
GEN lisp/ffap-tests.log
ELC lisp/filenotify-tests.elc
GEN lisp/filenotify-tests.log
ERROR: Job failed: exit code 137
failed
test-filenotify-gio Test
  ELC      hexl.elc
ELC hfy-cmap.elc
ELC hi-lock.elc
ELC hilit-chg.elc
ELC hippie-exp.elc
ELC hl-line.elc
ELC htmlfontify.elc
ELC ibuf-ext.elc
ERROR: Job failed: exit code 137