Remove TestRandom (#9006)

We  have a legacy `TestRandom` trait which generates random types for testing and fuzzing.
This function overlaps with `arbitrary` which is used very commonly in the ecosystem.


  Remove `TestRandom` and generate random type instances using `Arbitrary`.


Co-Authored-By: Mac L <mjladson@pm.me>

Co-Authored-By: Michael Sproul <michael@sigmaprime.io>

.github/forbidden-files.txt

@@ -12,4 +12,6 @@ beacon_node/http_api/src/block_rewards.rs
 common/eth2/src/lighthouse/attestation_performance.rs
 common/eth2/src/lighthouse/block_packing_efficiency.rs
 common/eth2/src/lighthouse/block_rewards.rs
+common/test_random_derive/
 consensus/types/src/execution/state_payload_status.rs
+consensus/types/src/test_utils/test_random/

.github/workflows/test-suite.yml

@@ -85,8 +85,8 @@ jobs:
             while IFS= read -r file || [ -n "$file" ]; do
               # Skip comments and empty lines
               [[ "$file" =~ ^#.*$ || -z "$file" ]] && continue
-              if [ -f "$file" ]; then
-                echo "::error::Forbidden file exists: $file"
+              if [ -e "$file" ]; then
+                echo "::error::Forbidden file or directory exists: $file"
                 status=1
               fi
             done < .github/forbidden-files.txt