temp tables are reflectable on the same session they were
created

that included non-alphabetic characters in the names, like dots or
spaces, would not be reflected with their name.
fixes #3495

``pg_catalog.pg_table_is_visible(c.oid)``, rather than testing
for an exact schema match, when the schema name is None; this
so that the method will also illustrate that temporary tables
are present.  Note that this is a behavioral change, as Postgresql
allows a non-temporary table to silently overwrite an existing
temporary table of the same name, so this changes the behavior
of ``checkfirst`` in that unusual scenario.
fixes #3264

kept separate from Postgresql's ON COMMIT for now even though ON COMMIT
is in the SQL standard; the option is still very specific to temp tables
and we eventually would provide a more first class temporary table
feature.
- oracle can apparently do get_temp_table_names() too, so implement that,
fix its get_table_names(), and add it to #3204.  fixes #3204 again.

Calls to reflect a table did not create any UniqueConstraint objects.
The reflection core made no calls to get_unique_constraints and as
a result, the sqlite dialect would never reflect any unique constraints.

MySQL transparently converts unique constraints into unique indexes, but
SQLAlchemy would reflect those as an Index object and as a
UniqueConstraint. The reflection core will now deduplicate the unique
constraints.

PostgreSQL would reflect unique constraints as an Index object and as
a UniqueConstraint object. The reflection core will now deduplicate
the unique indexes.

:meth:`.Inspector.get_temp_view_names`; currently, only the
SQLite dialect supports these methods.    The return of temporary
table and view names has been **removed** from SQLite's version
of :meth:`.Inspector.get_table_names` and
:meth:`.Inspector.get_view_names`; other database backends cannot
support this information (such as MySQL), and the scope of operation
is different in that the tables can be local to a session and
typically aren't supported in remote schemas.
fixes #3204