perf(ab_test): ignore noisy network and MMDS metrics on flaky instances

Add m5n.metal (al2 host), m8g.metal-{24,48}xl, and m8i.metal-{48,96}xl
to the IGNORED list for network latency and MMDS A/B tests respectively.

These instance/metric combinations exhibit high variance (up to 67%
swings in both directions) on unrelated commits, causing persistent
false-positive pipeline failures. The noise on m8g correlates with the
May 2 AL2023 rootfs update and affects only guest kernel linux-6.1
dimensions. MMDS noise on m8i is bidirectional within the same build.

The tests still run and collect data on these instances; they just no
longer block the pipeline.

Signed-off-by: Riccardo Mancini <mancio@amazon.com>

Author: Manciukic

tools/ab_test.py

@@ -135,6 +135,18 @@ def format_with_reduced_unit(value, unit):
         }
         for instance in ["m8i.metal-48xl", "m8i.metal-96xl"]
     ],
+    # Network latencies on m5n.metal w/ al2 host
+    {"instance": "m5n.metal", "performance_test": "test_network_latency", "host_kernel": "linux-5.10"},
+    # Network latencies on m8g
+    *[
+        {"instance": instance, "performance_test": "test_network_latency"}
+        for instance in ["m8g.metal-24xl", "m8g.metal-48xl"]
+    ],
+    # MMDS metrics on m8i
+    *[
+        {"instance": instance, "performance_test": "test_mmds_performance"}
+        for instance in ["m8i.metal-48xl", "m8i.metal-96xl"]
+    ],
     # block latencies if guest uses async request submission
     {"fio_engine": "libaio", "metric": "clat_read"},
     {"fio_engine": "libaio", "metric": "clat_write"},