CHORE: Add tests for Leaky MetaOperator

Context

The goal of this PR is to add tests for the Leaky SNN Metaoperator. As a metaoperator, it was dependent on the implementations of the operators it is made of. With the merge of Heaviside in dev, we can now add tests.

Modified files

• unit_tests/operator/Test_MetaOperator.cpp : add tests for Leaky operator.

Detailed major modifications

Add two tests sections to Test_MetaOperator :

• Leaky(forward)(fixed) : Test the leaky operator by comparing it to values previously computed using snntorch.
• Leaky(forward) : Test the leaky operator with random values (note that hyperparameters like beta are still fixed), comparing it to an ad-hoc implementation of the leaky operation.