parts.partition_float_myisam, parts.partition_int_myisam,
parts.partition_float_innodb are all known to fail with timeouts
on slow builders. The tests are composed of several independent parts
for corresponding subtypes (float == float + double,
int == tinyint + smallint + mediumint + int + bigint). The solution
is to split them into separate tests. No test logic has been changed.