Create pure Compose components for the editor and possibly the textview

[jmartinesp]

With the changes in this PR it would be possible to move our UI implementation in the Compose library from using a legacy View to actually building a full Compose solution, reusing our custom InputConnection implementation.

This would make the integration of the RTE in apps using Compose quite easier and solve a few issues we've seen.

There have also been some talks about generating the AnnotatedStrings/Spans from the Rust part of RTE library, so some work might overlap.