Which Buddhist schools give importance to cultivation of Jhanas? Which schools/lineages in Buddhism give importance to the cultivation of Jhanas before entering Vipassana, and which schools focus entirely on Vipassana?
This is not an exhaustive or scholarly answer, but:

Lineages or traditions don't necessarily predict how this is taught. I believe Ajahn Brahmavamso, who teaches that it's very important to master jhanas first, comes from the Thai Forest Tradition, but not all Thai Forest teachers emphasize that as strongly. Pa Auk Sayadaw in Burma is also a proponent of jhana mastery before vipassana.

On the other side of things, the Mahasi Sayadaw lineage in Burma emphasizes vipassana from the outset.

All traditions would agree (I think) that a certain degree of samatha is a prerequisite for attaining vipassana knowledges. The difference is in how one teaches the practice, and how strictly one defines 'jhana'. There is always a dynamic interplay between samatha and vipassana, so jhana factors can emerge in formal vipassana practices, and insight wisdom can develop during formal samatha practices.