Update to previous patch according to reviewers comments.

Removing parts.partition_alter4_innodb from default.experimental
(Also closed bug#45299 as a duplicate of bug#56659 as a result of this.)
Adding run of tests requiring --big-test flag to default.weekly to keep the coverage.

mysql-test/collections/default.experimental:
  Removed partition_alter4_innodb since it now requires --big-test flag to run
  since it is very time consuming.
mysql-test/collections/default.weekly:
  Added run of test that require --big-test flag, to be run on weekly basis.