Add ability to connect to redshift using DescribeClusters and GetClusterCredentialsWithIAM apis

[Tmonster]

Currently to attach to redshift, you need to url, host, port, username, and password (maybe more).

This information can all be made available if you call the DescribeClusters API with the redshift cluster name.

Once you have that information, you can also get credentials with IAM credentials using the GetClusterCredentialWithIAM apis.

This PR rolls accessing this logic into the AWS extension, and can allow users to attach to redshift with a simple ATTACH '<cluster_name>' AS redshift (TYPE redshift);

This needs more tests in the following areas

• authentication (STS, assuming roles etc.)
• failure modes
• incorrect region
• scoping secrets to redshift connection string

[Tmonster]

For some reason, adding duckdb_postgress is causing weird build issues in CI. Will have to take a deeper look soon