bugfix: schemas/util.sql: explain(): don't display any log messages printed by IMMUTABLE functions in the query, which EXPLAIN apparently runs

schemas/util.sql: create_if_not_exists(): added relation param, which can be used to ensure that a standard exception is always generated if the relation exists, even if the table definition would be invalid (which generates a variety of exceptions)

bugfix: schemas/util.sql: try_cast(), is_castable(): also need to handle syntax_error_or_access_rule_violation, which is thrown by ::regclass

schemas/util.sql: added relation_exists()

schemas/util.sql: save_drop_views()/restore_views(): store the view path in addition to the definition so it can be used in restoring

bugfix: schemas/util.sql: in_reverse(): can't use `SELECT *` for composite types because this expands them

bugfix: schemas/util.sql: array_reverse(): can't use `SELECT *` for composite types because this expands them

schemas/util.sql: save_drop_views()/restore_views(): use opaque return type so it can be changed without changing the local var type in functions that use this

schemas/util.sql: force_recreate(): recreate_users_cmds: renamed to restore_views_info since this is now whatever is needed by util.restore_views()

schemas/util.sql: added restore_views() and use it in force_recreate()