Extract navigation-fragments module from core module

[jayohms]

This PR extracts all the navigation + fragment concerns into a separate navigation-fragments module, so it's completely isolated from the core module. This new module will need to be consumed as a separate dependency by apps to obtain all the navigation + fragment features.

The core module now only includes the basic Turbo + Bridge APIs and all their WebView concerns.

This sets us up in the future to introduce new navigation/compose modules that can be used by an app instead of the navigation-fragments module. The core module now has no knowledge of navigation concerns or references to fragments.

The navigation-fragments module depends on core, but not the other way around. Since apps can now configure their entire app using the Hotwire.* object (see DemoApplication.kt), I had to separate the configuration namespace into two parts:

• navigation-fragments module: Hotwire.*
• core module: HotwireCore.*

This allows the core module to access configuration options related to core features and the navigation-fragment module to access all configuration options.

There's still future work that can be done to consolidate some code across the two modules, but from what I can tell those are all internal code concerns — not a public API concern. So we can continue to chip away at simplifying/streamlining down the road. Feel free to note any opportunities you see, but I may prefer to perform that work in future PRs if the public API isn't affected.

Note: I recommend pulling down the project so you can see the whole module structure so it's easier to the organization and packages.

Another note: I haven't setup artifact publishing support for this new module yet. I'll worry about that in another PR.

Closes #43

[jayohms]

cc @jhutarek mentioning you here, since I can only request one reviewer (while the repo is still private)

[mbarta]

Looks good 💪 I only left a couple of suggestions ;)