feat: enable opt-level-3 (#898)

In the EVM at least, this leads to a 60% speedup. Of course, that's a
pathological case, but still.

In terms of binary size, this increases the miner (largest) binary from
~1.2 to ~1.4MiB, but that's not a huge issue.

Author: Stebalien

Cargo.toml

@@ -92,7 +92,7 @@ inherits = "release"
 panic = "unwind"
 overflow-checks = true
 lto = "thin"
-opt-level = "z"
+opt-level = 3
 strip = true
 codegen-units = 1
 incremental = false