Create an AWS test account reservation service

[depombo]

[depombo]

Currently, every module has a dedicated test account with credentials given via Github Actions secrets and every test run picks an AWS regions within that test account via https://github.com/iasql/iasql-engine/blob/main/.github/workflows/ci.yml#L84.

As a precursor to support multiple regions in a single database, every test run will need to be given its own AWS account by this name reservation mechanism instead of having a dedicated test account per module. At the start of a test run, the CI job that currently picks a region semi-randomly should instead ask the stateful account reservation service for an available account (and its respective credentials) and make sure that no other test run uses it. In this way the input into tests, credentials passed via environment variables doesn't change, and neither those local development.