instead of panicking
We need to mve stuff in the parent element and that doesn't work if
it is a repeated element. Also there would not be ways to call show
on it anyway.
Fixes#1079
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.
