Provide an API mechanism to find the EPSILON associated with a given Tensor DType

[crutcher]

Feature description

Many numeric algorithms are defined up-to EPSILON equivalence; and lacking a well defined EPSILON for the various DTypes, it is difficult to write precise numeric algorithms, to test them, or to identify situations in which regression occurred.

Perhaps adding EPSILON to ElementLimits?

Feature motivation

Writing precise numeric code.

(Optional) Suggest a Solution

Perhaps adding EPSILON to ElementLimits?