repair any_() / all_() "implicit flip" behavior for None

repair any_() / all_() "implicit flip" behavior for None

Fixed an inconsistency in the any_() / all_() functions / methods where the
special behavior these functions have of "flipping" the expression such
that the "ANY" / "ALL" expression is always on the right side would not
function if the comparison were against the None value, that is,
"column.any_() == None" should produce the same SQL expression as "null()
== column.any_()". Added more docs to clarify this as well, plus mentions
that any_() / all_() generally supersede the ARRAY version "any()" /
"all()".

Fixes: #7140
Change-Id: Ia5d55414ba40eb3fbda3598931fdd24c9b4a4411