[mlir] Add sectionMemoryMapper to ExecutionEngineOptions

By specifying a sectionMemoryMapper, users can control how
memory for JIT code is allocated.

In particular, I need this in order to use a named memory
region so that profilers such as perf(1) can correctly label
execution cycles coming from JIT'ed code.

Reviewed-by: ezhulenev

Differential Revision: https://reviews.llvm.org/D120415