chore: Remove duplicate work in snapshot tests

[lym953]

Motivation

The command npx tsc --project tsconfig.json compiles the TypeScript test stacks into JavaScript code. Right now it's run once for every stack, which is unnecessary.

What does this PR do?

Only run this command once at the beginning.

Testing Guidelines

Step

1. Run and time the snapshot tests: time aws-vault exec sso-serverless-sandbox-account-admin -- scripts/run_integration_tests.sh

Result

Before:

60.37s user 6.44s system 116% cpu 57.561 total

After:

16.10s user 3.61s system 62% cpu 31.789 total

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