Various hardening for commonutils library internal calls for fuzzing #857

All 170 tests pass in 13m 32s

16 files - 28 91 suites +47 13m 32s ⏱️ - 26m 7s
170 tests + 166 170 ✅ + 166 0 💤 ± 0 0 ❌ ±0
2 210 runs +2 034 2 210 ✅ +2 056 0 💤 - 22 0 ❌ ±0

Results for commit adf4bdc. ± Comparison against earlier commit 1eeecc2.