rust: centralize config in workspace root This commit bundles common config option in the workspace root and applies them through <config>.workspace = true Signed-off-by: Stefan Zabka <git@zabka.it> Link: https://lore.kernel.org/r/20250502212748.124953-1-git@zabka.it Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>