Remove BaseIcebergConnectorTest.dropTable method

[ebyhr]

Description

BaseConnectorTest#testDropTable ensures non-existence of the table after dropping. No need to verify that in each test.

Also, getQueryRunner().tableExists was misused in testPartitionedTableStatistics. The method always returns false if we pass qualified table names.

Release notes

(x) This is not user-visible or is docs only, and no release notes are required.

[oneonestar]

(NIT)

I think

dropTable(tableName);
dropTable("test_create_partitioned_table_as");

is easier to read than:

assertUpdate("DROP TABLE " + tableName);
assertUpdate("DROP TABLE " + "test_create_partitioned_table_as");

[wendigo]

Can we instead use a TestTable here?

[ebyhr]

@wendigo Yes, but let me handle in follow-up.