assert: AssertionError difference on custom message

Addition of the error difference (actual and expected) when provided a custom message

Fixes: https://github.com/nodejs/node/issues/48465

Tests failing- test/parallel/test-debugger-restart-message.js test/parallel/test-policy-crypto-default-encoding.js test/parallel/test-policy-integrity-flag.js test/parallel/test-policy-dependencies.js test/parallel/test-policy-dependency-conditions.js test/parallel/test-policy-parse-integrity.js test/parallel/test-policy-manifest.js test/parallel/test-policy-scopes.js test/parallel/test-policy-scopes-dependencies.js test/parallel/test-policy-scopes-integrity.js test/node-api/test_policy/test_policy.js

All of the "policy" tests pass if I run them individually, I don't fully understand If I am doing something wrong.

PS- This is my first time contributing to open source, any help will be appreciated thanks! 👍