Schema::tableExists does not find views for PostgreSQL

Actually I think the default behavior is wrong. tableExists() method should not look for views. First of all it's not comply with its name. Second it causes errors when doing schema alterations as other Schema methods relies on tableExists().

A simple example to demonstrate the problem.

$schema = \Drupal::database()->schema();

if ($schema->tableExists('some_view')) {
  $schema->dropTable('some_view');
}

The above code returns the following error on MySQL database.

  SQLSTATE[42S02]: Base table or view not found: 1965 'd10.some_view' is a view  

Fixes are made on on 11.x (our main development branch) first, and are then back ported as needed according to our policies.