GeezerVison

Merge every located break that a new rangebreak overlaps, so that the located breaks never overlap.

Closes #7270. The same cause gives the symptoms in #5783 and in plotly/plotly.py#2998.

Cause: if a new break overlapped two located breaks, addBreak in ax.locateBreaks widened the two breaks but did not merge them. setScale and calcBreaksLength sum the break lengths, so they counted the overlap two times. A holiday between two overnight breaks thus adds 24 extra hours:

• The figure in Plot does not appear in some cases if rangebreaks overlap #7270 gets 100.5 h of breaks on a 99.5 h range, and the plot does not appear.
• The candlestick in y-values overlap when using rangebreaks  plotly.py#2998 gets 360 h of breaks instead of 336 h, and the candles after Christmas draw over earlier candles.

Fix: addBreak keeps the first overlapped break, extends it to the union, and removes the other overlapped breaks. If a new break overlaps zero or one located break, the output does not change.

Tests: a new spec in axes_test.js (*rangebreaks* > during setConvert) fails on main and passes with the fix. Other suites that use rangebreaks: range_slider, cartesian_interact, hover, draw_newshape, draw_newselection. The 24 image mocks with rangebreaks give the same located breaks before and after the fix, so no baseline changes.

Before (v4.2.0)	After