ruby-mode: Support endless methods (bug#54702)

ruby-mode: Support endless methods (bug#54702)

* lisp/progmodes/ruby-mode.el (ruby-endless-method-head-re):
New constant.
(ruby-smie-grammar): New token.
(ruby-smie--forward-token, ruby-smie--backward-token):
Recognize it.
(ruby-smie-rules): Indentation support.
(ruby-add-log-current-method): Support here too.

* test/lisp/progmodes/ruby-mode-tests.el
(ruby-add-log-current-method-after-endless-method): New test.

* test/lisp/progmodes/ruby-mode-resources/ruby.rb: New examples.