rust: reduce binary size by enabling the keccak no_unroll flag

Currently, firmware multi on master is 767888 bytes. By enabling this
feature, it's reduced to 766360 (1528 bytes savings).

https://docs.rs/keccak/latest/keccak/ also mentions tiny-keccak. I
tried this too and it resulted in a binary size of 766788 bytes, so
slightly larger than using the current sha3 crate we use.

Author: benma

src/rust/Cargo.lock

@@ -34,6 +34,10 @@ hex = { version = "0.4", default-features = false, features = ["alloc"] }
 num-bigint = { version = "0.4.6", default-features = false }
 sha2 = { version = "0.10.8", default-features = false }
 sha3 = { version = "0.10.8", default-features = false }
+# We don't rely on this dep directly, the sha3 dep does. We list it here to enable the
+# no_unroll feature to reduce the binary size, saving around 1528 bytes (as measured at time of
+# writing, this might fluctuate over time).
+keccak = { version = "0.1.4", default-features = false, features = ["no_unroll"] }
 zeroize = "1.7.0"
 
 [patch.crates-io]

src/rust/Cargo.toml

@@ -36,6 +36,7 @@ streaming-silent-payments = { path = "../streaming-silent-payments", optional =
 hex = { workspace = true }
 sha2 = { workspace = true }
 sha3 = { workspace = true, optional = true }
+keccak = { workspace = true, optional = true }
 digest = "0.10.6"
 zeroize = { workspace = true }
 num-bigint = { workspace = true, optional = true }
@@ -71,6 +72,7 @@ ed25519 = [
 app-ethereum = [
   "dep:erc20_params",
   "dep:sha3",
+  "dep:keccak",
   "dep:num-bigint",
   "bitbox02/app-ethereum",
 ]