fix: EXPOSED-173 UPDATE_RULE read incorrectly for Oracle

[joc-a]

Although the documentation of the driver mentions UPDATE_RULE here, it is missing from the ALL_CONSTRAINTS view here. Only DELETE_RULE is mentioned.

This is part of the SQL that runs when OracleDatabaseMetadata.getImportedKeys() is invoked:

SELECT NULL AS pktable_cat,
p.owner as pktable_schem,
p.table_name as pktable_name,
pc.column_name as pkcolumn_name,
NULL as fktable_cat,
f.owner as fktable_schem,
f.table_name as fktable_name,
fc.column_name as fkcolumn_name,
fc.position as key_seq,
NULL as update_rule,
decode (f.delete_rule, 'CASCADE', 0, 'SET NULL', 2, 1) as delete_rule
...

update_rule is hardcoded to NULL, which gets converted to 0 when using getInt("UPDATE_RULE"), and is then mistakenly taken to represent DatabaseMetaData.importedKeyCascade = 0.