Deprecate and remove `database.aws.crossplane.io` in favor of `rds.aws.crossplane.io`

[MisterMX]

What problem are you facing?

Currently, there are two separate implementations for RDS DBInstances:

• the hand-written RDSInstance.database.aws.crossplane.io and
• the ACK-generated DBInstance.rds.aws.crossplane.io

How could Crossplane help solve your problem?

To be consistent with AWS API Names, provider-aws should drop the database group in favor of rds. All features that are missing in rds should be ported from the legacy controller and added to the existing API.