Return effective trim point LSN on successful trim request #7989

All 44 tests pass, 1 skipped in 1m 58s

5 files - 2 5 suites - 2 1m 58s ⏱️ - 2m 35s
45 tests - 2 44 ✅ - 2 1 💤 ±0 0 ❌ ±0
113 runs - 69 111 ✅ - 68 2 💤 - 1 0 ❌ ±0

Results for commit d55eee4. ± Comparison against earlier commit 97beb75.