AP_NavEKF3: add gyro bias state inhibit and rework index limit calculation

Inhibiting gyro bias estimation during the initial tilt alignment speeds alignment.
The calculation of the maxmum state index required has been modified so that it can handle all combinations of inhibited states.
Limiting the maximum state index accessed by all EKF operations result in significant processing reductions when higher index states are not being used.

libraries/AP_NavEKF3/AP_NavEKF3_Control.cpp

@@ -161,12 +161,20 @@ void NavEKF3_core::setWindMagStateLearningMode()
 
     // Adjust the indexing limits used to address the covariance, states and other EKF arrays to avoid unnecessary operations
     // if we are not using those states
-    if (inhibitMagStates && inhibitWindStates && inhibitDelVelBiasStates) {
+    if (inhibitWindStates) {
-        stateIndexLim = 12;
+        if (inhibitMagStates) {
-    } else if (inhibitMagStates && !inhibitWindStates) {
+            if (inhibitDelVelBiasStates) {
-        stateIndexLim = 15;
+                if (inhibitDelAngBiasStates) {
-    } else if (inhibitWindStates) {
+                    stateIndexLim = 9;
-        stateIndexLim = 21;
+                } else {
+                    stateIndexLim = 12;
+                }
+            } else {
+                stateIndexLim = 15;
+            }
+        } else {
+            stateIndexLim = 21;
+        }
     } else {
         stateIndexLim = 23;
     }