[Deployment] Parallelize build and conditional deployment

[heitorlessa]

sam build can run in parallel to improve deployment time - Currently it runs sequentially for every stack.

[heitorlessa]

SAM CLI now supports parallel builds as well as cache. This means, we could make use of CI Cache + SAM CLI build and parallel to make deployment quicker.

Two other fundamental changes to cut down deployment time until that will enable a future work of one pipeline per service are:

• [ ] Only trigger deployments for services that changed (+ shared, until they're localized)
• [ ] Convert CI Parameter Store requests into a batch request. For those not being used as deployment time dependency for other stacks, for example integ/perf tests can be turned into a Map instead of multiple parameters