move `ArtifactKind` consts back into update-common

[iliana]

tufaceous/artifact/src/lib.rs

Lines 104 to 117 in bbadc27

	/// These artifact kinds are not stored anywhere, but are derived from stored
	/// kinds and used as internal identifiers.
	impl ArtifactKind {
	/// Gimlet root of trust bootloader slot image identifier.
	///
	/// Derived from [`KnownArtifactKind::GimletRotBootloader`].
	pub const GIMLET_ROT_STAGE0: Self =
	Self::from_static("gimlet_rot_bootloader");
	/// Gimlet root of trust A slot image identifier.
	///
	/// Derived from [`KnownArtifactKind::GimletRot`].
	pub const GIMLET_ROT_IMAGE_A: Self =
	Self::from_static("gimlet_rot_image_a");

These aren't tufaceous's jurisdiction. (Well, unless we make composite artifacts self-describing.)