Rust

Add bindings for seq.++ and seq.unit #555

Job	Run time
build (macos-latest)	55s
build_on_wasm	35m 47s
build_with_bundled_z3 (linux)	16m 25s
build (ubuntu-latest)	28s
build_with_vcpkg_installed_z3 (linux)	29m 13s
build_with_bundled_z3 (macos)	14m 38s
build_with_vcpkg_installed_z3 (macos)	12m 21s
build_with_bundled_z3 (windows)	19m 29s
check-formatting	6s
build_with_vcpkg_installed_z3 (windows)	44m 46s
run_clippy	27s
	2h 54m 35s

Provide feedback