Optimize allocations

• fixed type instability in SRHD project
• dropped the mesh kw argument in the @with_signature function signature, which was a left over from the legacy mode, x-ref !93 (merged)
• slapped on some @inlines; the most important one was inside broadcast_computations as it removed allocations
• disabled @timeit inside the broadcasting methods, because they seem to introduce spurious allocations
• added a few @views in random places

I did not benchmark the run time improvement, but at least now allocs in rhs calls are mostly zero, as they should be.