d/rules: switch to cargo wrapper

notable differences:

using dh-cargo for dh-cargo-built-using instead of dh-rust for dh-rust-built-using (the latter was generating incomplete information)

cargo test now no longer invoked with --release - this usually increases test coverage, as additional compiler checks which are only enabled in dev/debug mode are used.

LTO thin is no longer forced via the config, it can be injected with DEB_BUILD_OPTIONS if desired

-dbgsym now actually contains debug symbols

Signed-off-by: Fabian Grünbichler git@fabian.gruenbichler.email