anchor.diff:      let chars = ArrayPool<char>.Shared.Rent sb.Length
       sb.CopyTo(0, chars, 0, sb.Length)
       let result = Encoding.UTF8.GetBytes(chars, 0, sb.Length)
  -    StringBuilderPool.Return sb
  +    StringBuilderPool.Release sb
       ArrayPool<char>.Shared.Return chars
       result
   
  
positive.code:     [<DefaultValue; ThreadStatic>]
      static val mutable private created : DateTimeOffset
  
      static member AlwaysCreateNew
          with get ()   = StringBuilderPool.alwaysCreateNew
          and  set flag = StringBuilderPool.alwaysCreateNew <- flag
  
      static member Rent () =
          match StringBuilderPool.AlwaysCreateNew with
          | true  -> new StringBuilder(MinimumCapacity)
          | false ->
              let lifetime = DateTimeOffset.Now - StringBuilderPool.created
              let expired  = lifetime > MaximumLifetime
              let sb       = StringBuilderPool.instance
  
negative.code:                 sb.Clear()
              else new StringBuilder(MinimumCapacity)
  
      static member internal Release (sb : StringBuilder) =
          if sb.Capacity <= MaximumCapacity then
              StringBuilderPool.instance <- sb
              StringBuilderPool.created  <- DateTimeOffset.Now
  