feat(visualization): add per-map option for top labels (#4487)

When more than one map is selected in standard mode, a new
'All maps | Per map' toggle in the label settings splits the
node-selecting label computations per map: top-N labels are picked
separately for each map (Height and Color mode), and overlapping
labels are only grouped within the same map. Hidden for a single
map and in delta mode; defaults to the previous global behavior.

Co-authored-by: Christian Hühn <christian.huehn@maibornwolff.de>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>