Amplify Console should be able to build only when certain files have been modified

**Is your feature request related to a problem? Please describe.**
It's annoying and a waste of resources to build & deploy if we modify files that have nothing to do with the code (e.g. README or unit tests)

**Describe the solution you'd like**
It would be great to have a solution like the one GitHub Actions offers, where we can specify multiple paths to check for modified files:

```yaml
on:
push:
branches:
- main
paths:
- 'src/**'
- 'infra/**'
- '.env*'
- 'cdk.context.json'
```

No implementation files, tests, or entry points are named. Start by locating the Amplify Console build and deployment configuration and comparing its capabilities with GitHub Actions path filters; done means unrelated changes such as README or unit-test edits no longer trigger a build, while changes in configured source or infrastructure paths still do.

Written by the indexing model from the issue text.