Increase dev mode opt-level for curve25519-dalek crate (#7220)

* increase dev mode opt-level for curve25519-dalek crate

* add comment to give context on bumping up the opt-level

Cargo.toml

@@ -1,6 +1,16 @@
 [profile.dev]
 split-debuginfo = "unpacked"
 
+# The curve25519-dalek crate uses the `simd` backend by default in v4 if
+# possible, which has very slow performance on some platforms with opt-level 0,
+# which is the default for `dev` and `test` builds. This slowdown causes
+# certain interactions in the solana-test-validator, such as verifying ZK
+# proofs in transactions, to take much more than 400ms, creating problems in
+# the test environment. To give better performance in the solana-test-validator
+# during tests and dev builds, override the opt-level to 3 for the crate.
+[profile.dev.package.curve25519-dalek]
+opt-level = 3
+
 [workspace]
 members = [
   "associated-token-account/client",