Always use lexical-binding in lisp-interaction-mode (bug#38835)

* lisp/progmodes/elisp-mode.el (lisp-interaction-mode):
Set lexical-binding.
* lisp/startup.el (command-line, startup--get-buffer-create-scratch):
Don't set lexical-binding here.
* doc/lispref/variables.texi:
* etc/NEWS:
Make it clear that lisp-interaction-mode uses lexical-binding.
1 job for emacs-27 in 54 minutes and 20 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #4747
test-all

00:54:20