Allow tile features to specify their height

[freundTech]

Currently the height of a tile card is specified by the number of features it has, with the same amount of vertical space given to every feature.

Letting features specify their own height would give more control to developers and enable new possibilities that previously required custom cards.

I specifically would like to write a custom feature that adds a vertical slider for use with covers (in contrast to the horizontal slider feature that is built in to Home Assistant).