feat(build/booter): support esm

[achrinza]

This PR introduces support for ESModules in @loopback/build and @loopback/boot.

Breaking changes:

• @loopback/build
  • tsconfig.common.json is updated to support hybrid CommonJS+ESModule packages. This prevents TypeScript from rewriting dynamic import()s into require()s, which is needed by @loopback/boot.
• @loopback/boot
  • loadClassesFromFiles now returns a Promise

Part of: https://github.com/loopbackio/loopback-next/issues/10744

Checklist

• [x] DCO (Developer Certificate of Origin) signed in all commits
• [x] npm test passes on your machine
• [x] New tests added or existing tests modified to cover all changes
• [x] Code conforms with the style guide
• API Documentation in code was updated
• Documentation in /docs/site was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in examples/* were updated

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