Use a faster median calculator for the range map's binary search.

It was inspired from .NET 5's span binary search and performs one less operation.
Perform array indexing only once in RangeMap.TryFind.
And designtime Farkles with metadata are now called designtime Farkle wrappers.

Author: teo-tsirpanis

Diff for: src/Farkle/Builder/DesigntimeFarkle.fs

@@ -173,7 +173,7 @@ type internal DesigntimeFarkleWrapper<'T> = {
 with
     static member Create (df: DesigntimeFarkle<'T>) =
         match df with
-        | :? DesigntimeFarkleWrapper<'T> as dfwm -> dfwm
+        | :? DesigntimeFarkleWrapper<'T> as dfw -> dfw
         | _ -> {InnerDesigntimeFarkle = df; Name = df.Name; Metadata = GrammarMetadata.Default}
     interface DesigntimeFarkle with
         member x.Name = x.Name

Diff for: src/Farkle/Collections/RangeMap.fs

@@ -51,7 +51,7 @@ type RangeMap<'key,'a when 'key :> IComparable<'key>> private(arr: RangeMapEleme
     // Adapted from .NET's binary search function.
     let rec binarySearch lo hi k =
         if lo <= hi then
-            let median = lo + (hi - lo) / 2
+            let median = int ((uint32 hi + uint32 lo) >>> 1)
             match arr.[median].KeyTo.CompareTo k with
             | 0 -> median
             | x when x < 0 -> binarySearch (median + 1) hi k
@@ -87,8 +87,9 @@ type RangeMap<'key,'a when 'key :> IComparable<'key>> private(arr: RangeMapEleme
                 // the next nearest element to be found. We also limit
                 // it to the highest index in the array.
                 | x -> Math.Min(~~~x, arr.Length - 1)
-            if arr.[idx].KeyFrom.CompareTo k <= 0 && k.CompareTo arr.[idx].KeyTo <= 0 then
-                ValueSome arr.[idx].Value
+            let element = &arr.[idx]
+            if element.KeyFrom.CompareTo k <= 0 && k.CompareTo element.KeyTo <= 0 then
+                ValueSome element.Value
             else
                 ValueNone
     /// A read-only span containing the elements of the range map.