New modules for RDS clusters management (ansible-collections#687)

New modules for RDS clusters management

SUMMARY

Two new modules for RDS clusters management (rds_cluster ans rds_cluster_info)
Took over from: ansible-collections#262
Depends-On: ansible-collections#553
Closes ansible-collections#849
Should also close ansible-collections#191

ISSUE TYPE

New Module Pull Request

Reviewed-by: Mark Woolley <mw@marknet15.com>
Reviewed-by: Alina Buzachis <None>
Reviewed-by: Markus Bergholz <git@osuv.de>

This commit was initially merged in https://github.com/ansible-collections/community.aws
See: ansible-collections/community.aws@3661b1c