Generate modern JS outputs that can be consumed by other JS toolchains (Blazor->JS)

* Users should be able to rely on standard JS idioms (import statements) to consume Blazor JS assets.
* **Our build system should be able to produce an output layout that can easily be consumed by JS tools.**
* For example, adding a package.json to the project and calling an `npm script` after Blazor's build/publish steps.
* This might simply mean we offer the option to link Blazor outputs into the dist/(Debug|Release) folders.

## Items
* Generate ES module bundles that can be consumed via import statements.
* Our modules should not pollute the global state (by default).
* Blazor web will have a base layer and separate chunks for enhanced nav, server interactivity, and wasm interactivity. Other Blazor flavors will be a single bundle.
* ~~Update the wasm loading strategy to rely on standard JS idioms that toolchains can understand with enough flexibility to adapt to different bundlers.~~
* ~~Standard import. E.g. import { Blazor } from 'blazor'~~
* ~~Import as URL. E.g. import system from './_framework/system.wasm?url' (then we do fetch(system.url) or similar to load the asset).~~
* ~~Fetch (we don't include an import, and inside the loader we use fetch directly to load the asset).~~