Add bloqs to resize int/fxp registers

[anurudhp]

#1162 implements SignExtend for resizing signed integers.

More bloqs to add (open to naming suggestions):

• Add ZeroExtend for resizing unsigned values
• Add ResizeInt for delegating to the appropriate signed/unsigned extension / truncation bloqs.
• Bloqs to resize Fxp values (integer part, fractional part)
• Use the above resize bloqs in arithmetic bloq implementations