Added rejection sampler based on sampling from untruncated normal for

parametrized_truncated_normal.

Modifies the behavior of all samplers to raise an Exception if no sample is
accepted (current behavior is returning a sample from a uniform
distribution which is confusing behavior). This situation should only arise
if none of the existing rejection samplers are a good fit for the parameter
regime.

PiperOrigin-RevId: 218254962