Fix for issue 1027

[MichaelHussey]

Description

Explicitly sets --REGION for all AWS commands when creating Postgres DB

Also bumped the database instance type to T3 as I got this error:

An error occurred (InvalidParameterCombination) when calling the CreateDBInstance operation: RDS does not support creating a DB instance with the following combination: DBInstanceClass=db.t2.micro, Engine=postgres, EngineVersion=13.3, LicenseModel=postgresql-license. For supported combinations of instance class and database engine version, see the documentation.
WARNING: Could not create database, troubleshoot and try again

This PR should also address

• https://confluentinc.atlassian.net/browse/DEVX-2421
• VPC issues

An error occurred (InvalidVPCNetworkStateFault) when calling the CreateDBInstance operation: Cannot create a publicly accessible DBInstance. The specified VPC has no internet gateway attached.Update the VPC and then try again

Author Validation

Describe the validation already done, or needs to be done, by the PR submitter.

• • cloud-etl

Reviewer Tasks

Describe the tasks/validation that the PR submitter is requesting to be done by the reviewer.

[MichaelHussey]

This also makes the DB publicly accessible.

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}