feat(datagrid): split result charts into one panel per column value

[datlechin]

Why

A result chart drew one plot. Comparing the same chart across regions or products took one query per value or an export.

Change

• Facet picker beside X, Y and Series: one chart per value, in a grid with shared axes and one legend. Up to 12 panels, in the query's order.
• A series keeps its color, symbol and dash in every panel and through a re-sort or page turn.
• Chart and map keep their drawing while a refresh, sort or page turn rebuilds it. The chart no longer shows the previous result's notices.
• Empty text reads "Empty" in chart labels, NULL no longer merges with a literal "No value", and a picker whose column left the result shows its none item instead of going blank.

Verified

New projector, canvas, pane state and layout tests cover each fix. The canvas tests for series color and bar slots across panels fail with the explicit scales and slot order taken out. ResultChartSelectionTests and one ResultChartProjectorTests case only follow renamed types.

Screenshots

Rendered from the chart views with ImageRenderer (a sandboxed build has no chart license). The chart type control is left out: ImageRenderer cannot draw it.

	Light	Dark
Facet: None
Facet: region

Not in this PR

• %d more and %d skipped have no French plural. Only 22 of 356 count strings do, so it needs one catalog pass.
• Facet takes text, boolean, enum and set columns, not an integer like a year.

Fixes #3348