chore: Add snapshot test for Go stacks

[lym953]

What does this PR do?

Add a Go stack to snapshot tests, so that the test will compare the snapshots generated after vs before, to check if a PR causes unexpected changes on the stack to be deployed.

The stack was copied from examples/go-stack. I had to copy it because I don't think it's possible to just reference the existing stack.

Motivation

Adding more tests to make it safer to deploy changes.

Testing Guidelines

To ensure the example stack uses the locally built Go package instead of the production package, I:

1. Add a line to applyEnvVariables() in env.ts:

lam.addEnvironment("Ah", "Oh");

so an extra environment variable will be added to the Lambda function.

2. Run yarn build
3. Run the snapshot test aws-vault exec sso-serverless-sandbox-account-admin -- scripts/run_integration_tests.sh

Result:
The test failed. The generated snapshot has the new environment variable, which captures the unintended change.

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog