Task 2.8: IAM-Based Auth for Dependencies

[jshiwamV]

• Setup IAM-auth Postgres and blob storage Use cloud IAM roles instead of static credentials.

• Validate Materialize can authenticate with them Test IAM roles from pods using Workload Identity or IRSA.

[jshiwamV]

IAM for blob storage is done for AWS / Azure. For GCP we need changes in environmentd. More details in this PR
#74.

Keeping this open since we will need to add changes for Postgres.