Commit 24dcef5fed added a warning for the
implicit export of last component. For 1.0, this commit makes it so that
the root component is determined by the last export in the file.
Move "internal" crates into the `internal` directory. This first batch
includes most of sixtyfps_runtime but leaves the rendering backends
alone for now.
pre-commit applied some cleanups to the moved files:
- Consistent newline at end of file policy
- trimming trailing whitespace
- Formatting Cargo.toml files.