Add entity name overlap tests

[dimas-b]

Following up on the discussion in #4148 (related to #4108), it seems valuable to add generic entity name collision tests to polaris-tests.

Previous work on this from @Subham-KRLX (class PolarisRestCatalogIntegrationBase):

  @Test
  public void testCreateTableNameThatCollidesWithNamespace() {
    Assumptions.assumeThat(testNamespaceTableNameCollision()).isTrue();

    Namespace parentNamespace = Namespace.of("ns1");
    restCatalog.createNamespace(parentNamespace);
    restCatalog.createNamespace(Namespace.of("ns1", "clash"));

    assertThatThrownBy(
            () ->
                restCatalog
                    .buildTable(TableIdentifier.of(parentNamespace, "clash"), SCHEMA)
                    .create())
        .isInstanceOf(AlreadyExistsException.class)
        .hasMessageContaining("already exists");
  }

Each name withing a namespaces should only map to at most one entity type (Table, (nested) Namespace, View, etc.)