LargeStrokeDirtyClipTest: use relative coords + refresh chart goldens

The test was using hard-coded iPhone-portrait coordinates
(bottom = y + 1714, xStep = 262.75) which drew the two polylines off
the bottom of the Android emulator's 320x640 viewport, so the Android
golden was an empty data area surrounded by the four opaque-black
margin strips. Switch to coordinates derived from getWidth() /
getHeight() so the same chart-line geometry (years 2018-2022, north
12,16,22,18,28; south 8,11,13,16,19) lands inside the data area at
any native resolution.

Also refreshes the 10 Android chart goldens against the post-fix
CI captures -- the previous Android baselines were committed on
2026-05-09 alongside an earlier transitional version of the chart
suite that pre-dated the chart Canvas alpha-leak fix in 4e3f8b4,
so they reflect the partial-renders the bug used to produce on
Android. The new captures show fully-rendered XYCharts (chart-line
shows both polylines + year labels + Year/Value axis titles +
North/South legend) matching the iOS GL and Metal goldens.

The two iOS graphics-large-stroke-dirty-clip baselines are dropped
in this commit; they used the old hard-coded coordinates and would
mismatch the next CI run. The next run will regenerate them.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: shai-almog