[MERGE] web: Various graph view improvements

This PR aims to bring several improvements to the graph view.

The main points are:
- custom tooltips in line mode to avoid problems with the Chart.js generic tooltips (those cannot
go outside of the canvas boundary and information is lost).
- tooltips when legend items hovered in case their texts were cut for reason of space.

See task https://www.odoo.com/web#id=1963306&action=333&active_id=133&model=project.task&view_type=form&menu_id=4720



closes odoo/odoo#33910

Signed-off-by: VincentSchippefilt <VincentSchippefilt@users.noreply.github.com>