Declare and document all five Scale draw stages - #12327

Description

Scale#draw dispatches to five methods, one per part of the axis (drawBackground, drawGrid, drawBorder, drawTitle, drawLabels), and RadialLinearScale overrides all five. The Scale type declares only three, and gives drawTitle a chartArea parameter neither call site passes, so a TypeScript scale cannot reach the other two through super and super.drawTitle() does not compile:

error TS2339: Property 'drawBackground' does not exist on type 'Scale<O>'.
error TS2554: Expected 1 arguments, but got 0.

This declares all five and documents them in docs/developers/axes.md. That is the part of #3214 still open: #8598 split the drawing into these methods, but they were never written down as the supported way to customize one part of an axis.

Narrowing drawTitle(chartArea: ChartArea) to drawTitle() is a types-only break for anyone who declared that parameter, though it has always been undefined at runtime. Happy to use chartArea?: ChartArea instead.

User-Facing Changes

None at runtime. TypeScript scales can now override all five draw stages, and the docs list them.

Tests

test/types/extensions/scale.ts overrides the five stages through super: the errors above before, tsc -p test/types clean after. A new Core.scale draw spec asserts the dispatch order and that drawTitle gets no arguments; making draw pass chartArea to it turns that spec red. Full suite 1704/1704, Chrome headless 148 on Linux.