Let hash functions take a digest::Digest trait

... and add adapters for current Sha512 implementations that does not inplement the Digest trait

embassy-boot/boot/src/digest_adapters/salty.rs

@@ -0,0 +1,29 @@
+use digest::typenum::U64;
+use digest::{FixedOutput, HashMarker, OutputSizeUser, Update};
+
+pub struct Sha512(salty::Sha512);
+
+impl Default for Sha512 {
+    fn default() -> Self {
+        Self(salty::Sha512::new())
+    }
+}
+
+impl Update for Sha512 {
+    fn update(&mut self, data: &[u8]) {
+        self.0.update(data)
+    }
+}
+
+impl FixedOutput for Sha512 {
+    fn finalize_into(self, out: &mut digest::Output<Self>) {
+        let result = self.0.finalize();
+        out.as_mut_slice().copy_from_slice(result.as_slice())
+    }
+}
+
+impl OutputSizeUser for Sha512 {
+    type OutputSize = U64;
+}
+
+impl HashMarker for Sha512 {}