Apply quoting to SQL Server _switch_db

Apply quoting to SQL Server _switch_db

Added identifier quoting to the schema name applied to the "use" statement
which is invoked when a SQL Server multipart schema name is used within  a
:class:`.Table` that is being reflected, as well as for :class:`.Inspector`
methods such as :meth:`.Inspector.get_table_names`; this accommodates for
special characters or spaces in the database name.  Additionally, the "use"
statement is not emitted if the current database matches the target owner
database name being passed.

Fixes: #4883
Change-Id: I84419730e94aac3a88d331ad8c24d10aabbc34af