Generate remarks for matrix operations in a function. To generate remarks

for matrix expressions, the following approach is used:

- Collect leafs of matrix expressions (done in RemarkGenerator::getExpressionLeafs). Leafs are lowered matrix instructions without other matrix users (like stores).

- For each leaf, create a remark containing a linearizied version of the matrix expression.

The following improvements will be submitted as follow-ups:

- Summarize number of vector instructions generated for each expression.
- Account for shared sub-expressions.
- Propagate matrix remarks up the inlining chain.