feat: consider using line search in hybrid strategy

[jolars]

I assume we want to avoid computing $\lVert X \rVert_2^2$ when $X$ is large, so even (especially) for the hybrid strategy it makes sense to do a line search for the step size.

[jolars]

This was on the table with #33 and #15 but we decided against incorporating it to keep the codebase clean.