feat: alternative fingerprint rules count once (4.8.0)

Discovery compares drivers by score divided by the most a driver could
score, and that maximum summed every positive rule. Rules that never
match together, such as one vendor's landing page or another's, made a
driver that knows several vendors lose to one that knows none:
napalm-redfish's Supermicro landing page scored 6 of 41 and lost to a
bare "linux" in the same BMC's SNMP sysDescr, 5 of 18.

FingerprintRule gets an optional group. rules_max_weight() sums the
positive rules and counts each group once, with its strongest rule.
Existing rules have no group and count as before.

tests/test_fingerprint_base.py

@@ -8,6 +8,7 @@ from napalm_device_types import (
     DeviceTypeDriver,
     FingerprintRule,
     FirewallDriver,
+    rules_max_weight,
     HypervisorDriver,
     OSDriver,
     PortSpec,
@@ -90,6 +91,53 @@ def test_fingerprint_rule_negative():
     assert r.negative is True
 
 
+def test_fingerprint_rule_has_no_group_by_default():
+    assert FingerprintRule("fritz!box").group is None
+
+
+def test_fingerprint_rule_group():
+    r = FingerprintRule("idrac", weight=6.0, group="landing_page")
+    assert r.group == "landing_page"
+
+
+# ── rules_max_weight: the most a set of rules can add ─────────────────────────
+
+def test_max_weight_sums_rules_that_can_match_together():
+    rules = [FingerprintRule("proxmox virtual environment", 9.0), FingerprintRule("pve", 2.0)]
+    assert rules_max_weight(rules) == 11.0
+
+
+def test_max_weight_counts_one_rule_per_group():
+    # Alternatives: a page is ATEN's or iDRAC's or iLO's, never all three. Summing
+    # them made a driver that knows three BMC families lose to one that knows none.
+    rules = [
+        FingerprintRule("aten international", 6.0, group="landing_page"),
+        FingerprintRule("idrac", 6.0, group="landing_page"),
+        FingerprintRule("integrated lights-out", 4.0, group="landing_page"),
+    ]
+    assert rules_max_weight(rules) == 6.0
+
+
+def test_max_weight_mixes_groups_and_single_rules():
+    rules = [
+        FingerprintRule("redfishversion", 10.0, group="redfish_answer"),
+        FingerprintRule("@message.extendedinfo", 8.0, group="redfish_answer"),
+        FingerprintRule("#serviceroot.", 5.0),
+        FingerprintRule("aten international", 6.0, group="landing_page"),
+        FingerprintRule("idrac", 6.0, group="landing_page"),
+    ]
+    assert rules_max_weight(rules) == 21.0
+
+
+def test_max_weight_ignores_negative_rules():
+    rules = [FingerprintRule("vcenter", 9.0), FingerprintRule("vmware esxi", 9.0, negative=True)]
+    assert rules_max_weight(rules) == 9.0
+
+
+def test_max_weight_of_no_rules_is_zero():
+    assert rules_max_weight([]) == 0.0
+
+
 def test_fingerprint_rule_is_immutable():
     r = FingerprintRule("test", weight=3.0)
     with pytest.raises(AttributeError):