nims: add initialize session(s) apis for generic and niswitch specific multiplexers #1735

All 606 tests pass, 9 skipped in 31m 11s

25 files ±0 25 suites ±0 31m 11s ⏱️ -16s
615 tests ±0 606 ✅ ±0 9 💤 ±0 0 ❌ ±0
12 265 runs ±0 11 160 ✅ ±0 1 105 💤 ±0 0 ❌ ±0

Results for commit 4ac486b. ± Comparison against earlier commit 469102b.