Formatter: add & to yielding methods without a block parameter

[HertzDevil]

Resolves part of #8764.

This is not done to macros because they don't overload by block presence; all macros may be called with or without a block, regardless of whether the macro yields, whether the block parameter exists, and whether that parameter has a name.

0a4474a adds a total of 553 anonymous block parameters to the repository this way.

[veelenga]

This change introduces a small issue formatting a method with inlined comments

def foo # my foo method
  yield 42
end

formats to

def foo # my foo method(&)
  yield 42
end

[straight-shoota]

Thanks for reporting. I created a new issue #13091 to track this.