apply basic escaping to anon_labels unconditionally

apply basic escaping to anon_labels unconditionally

Fixed issue which prevented the :func:`_sql.literal_column` construct from
working properly within the context of a :class:`.Select` construct as well
as other potential places where "anonymized labels" might be generated, if
the literal expression contained characters which could interfere with
format strings, such as open parenthesis, due to an implementation detail
of the "anonymous label" structure.

Fixes: #8724
Change-Id: I3089124fbd055a011c8a245964258503b717d941