Add support for webpack dev server to inject in-memory build assets into AEM served pages

### Expected Behaviour

Webpack dev server should proxy content pages from AEM and inject it's in-memory assets in the page. This way the dev server will create the bundles in memory. Webpack provisioned clientlibs should not be proxied.

For the ui.frontend.react, this requires rewiring the CRA Webpack config.

### Actual Behaviour

Webpack dev server only proxies, but still requires a build to provision the clientlibs. Live reloading is not supported with watch.

### Reproduce Scenario (including but not limited to)

#### Steps to Reproduce

Make a code change in ui.frontend. To see the changes on an AEM page, a Webpack build is required, then the clientlibs need to be built, and then the clientlibs need to be synced to the local instance.

#### Platform and Version

AEM

#### Sample Code that illustrates the problem

#### Logs taken while reproducing problem

The issue names ui.frontend.react and the webpack dev server but no implementation files or tests. Start by reproducing the current AEM proxy and clientlib-sync workflow; done means AEM content pages use in-memory webpack assets, webpack-provisioned clientlibs are not proxied, and changes appear without a build and sync.

Written by the indexing model from the issue text.