updating Roda template synth script and fixing rds.DatabaseInstanceProps credentials prop

[arozar]

Commit 1 - updating Roda table and database names for template synth script

Description of changes: The file SynthRodaTemplates.sh has incorrect naming of glue tables and database names that are created using the Cloudformation stacks that are suggested in comments at the bottom of the script.

Commit 2 - updating rds.DatabaseInstanceSourceProps to use credentials object

Description of changes: Currently, the Typescript is no longer compiling.

This is due to the fact the rds.DatabaseInstanceProps interface now uses a credentials property rather than a username and password properties.

Have tested by doing the following:

• Code now compiles
• Deployed the environment and the SSM run command scripts are now able to use the dbSecrets to seed data in the RDS instances.

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