compose: functional tests

[weikanglim]

Functional tests (programmatic flow)

Add functional tests that take an azure.yaml as input and validate the output bicep from azd infra synth.

Consider if snapshot testing is appropriate. The minimum is running bicep build to ensure its syntactically sound.

In the future, we can consider add live testing to the appropriate scenarios.

This should replace scaffold_test.go

Functional tests (user driven flow)

Add UI tests that take a string of input representing the user interactions and validate that azd infra synth on the resulting azure.yaml succeeds.

We'll use this to cover most code path scenarios