Random Dialect Cleanups

[asraa]

• Remove num_bits from PRNG specification, lower level dialects closer to the implementation should support this
• Potentialy if random is a high level abstraction class, maybe we just need to have the sample op? Perhaps the source of randomness is also an implementation choice at a lower level

[lawrencekhlim]

Will also need to adjust #874 when removing num_bits and other adjustments to Random Dialect.