Make `cargo run` always available for binaries
Previously, items for `cargo test` and `cargo check` would appear as in
the `Select Runnable` quick pick that appears when running
`rust-analyzer: Run`, but `run` would only appear as a runnable if a
`main`` function was selected in the editor. This change adds `cargo
run` as an always available runnable command for binary packages.
This makes it easier to develop cli / tui applications, as now users can
run application from anywhere in their codebase.