Add a `dialect_registration` callback for "translations" registered with mlir…

Authored by mehdi_amini on Aug 22 2020, 5:57 PM.


Add a dialect_registration callback for "translations" registered with mlir-translate

This will allow out-of-tree translation to register the dialects they expect
to see in their input, on the model of getDependentDialects() for passes.

Differential Revision: https://reviews.llvm.org/D86409