FastMath.toMultipleOf should be renamed to FastMath.alignToPowerOfTwo

[riccardobl]

See: #1782 (comment)

The FastMath.toMultipleOf , used by the ubo implementation, only works for p that is a power of two, this can be confusing for devs looking to use FastMath apis in their code.

It should be renamed to alignToPowerOfTwo, and a generic implementation for toMultipleOf should be provided in place of the current one.