Expand reg for schema translate map for most special characters

Expand reg for schema translate map for most special characters

Fixed regression where usage of a token in the
:paramref:`_engine.Connection.execution_options.schema_translate_map`
dictionary which contained special characters such as braces would fail to
be substituted properly. Use of square bracket characters ``[]`` is now
explicitly disallowed as these are used as a delimiter character in the
current implementation.

Fixes: #6216
Change-Id: I7ccfc2292b17340054cedf485ed1adf3119b96c8