CI: Try to speed up the loom tests even more (#2187)

Not sure if this will actually help, but I don't think it will hurt.

Author: smalis-msft

Cargo.toml

@@ -603,9 +603,11 @@ lto = 'fat'
 [profile.dev.package.minimal_rt]
 opt-level = 1
 
-# Optimize loom even in the dev profile, as otherwise tests just take too long.
+# Optimize loom and its main dependency even in the dev profile, as otherwise tests just take too long.
 [profile.dev.package.loom]
 opt-level = 3
+[profile.dev.package.generator]
+opt-level = 3
 
 [patch.crates-io]
 # Pending <https://github.com/ferrilab/bitvec/pull/273>