- Use latest stable for rustfmt and clippy.
- Update Rust in rust-toolchain and coredeps Docker container to 1.54.0
and test against it.
- Test against 1.48.0 to ensure libdeltachat can be compiled with Debian
bullseye "rustc" and "cargo".
Rust does not work on manylinux2010 due to old GNU C Library.
We have been using manylinux2014 on CI machine already, but this change
was never commited.