* Add unsigned variants for BitConverter bit APIs

Adds DoubleToUInt64Bits, UInt64BitsToDouble, SingleToUInt32Bits,
UInt32BitsToSingle, HalfToUInt16Bits and UInt16BitsToHalf.

Implementations were based on existing signed integer variants.

Convert usages of existing APIs to unsigned variants when appropriate.

Fix #36469

* Revert comment change

Reverted a comment change made in the existing code by mistake.

* Use existing code for implementations

Use the existing signed methods with a cast, less code with the same codegen.

* Cast correction

Corrected the type used in a cast.