[skia-sync] Merge upstream chrome/m150

[mattleibow]

Automated upstream merge of chrome/m150.

mono/skia: Upstream merge chrome/m150 into skiasharp

Overview

Merges upstream chrome/m150 (commit 86bafa2700) into the skiasharp fork branch.
This brings in Skia milestones 148, 149, and 150.

Upstream merge commit

76b88362da — "Merge upstream chrome/m150 into skiasharp"

Conflict resolutions

File	Resolution
DEPS	Kept our pinned deps (expat 2.8.1, freetype, harfbuzz 14.2.0, libjpeg-turbo 3.1.4.1, libpng 1.6.58, libwebp, zlib 1.3.2.1, vulkanmemoryallocator, vulkan-headers); accepted upstream structure changes for brotli/skcms/dawn
include/core/SkFont.h	Combined: kept fork-specific breakText() overloads AND added upstream makeStrikeRef() method from m150
RELEASE_NOTES.md	Took upstream (adds m148/m149/m150 release notes)
include/utils/SkEventTracer.h	Took upstream (updated onExit() comment)
src/utils/SkEventTracer.cpp	Took upstream (adds atexit([]() { GetInstance()->onExit(); }) in SetInstance())
src/core/SkPixmap.cpp	Took upstream (upstream adopted our RGBA/BGRA fix)
src/core/SkRuntimeEffect.cpp	Took upstream
src/gpu/graphite/mtl/MtlCaps.mm	Took upstream (Graphite — not used by SkiaSharp)
third_party/harfbuzz/BUILD.gn	Kept ours (matches our pinned HarfBuzz 14.2.0)
modules/skcms/version.sha1	Took upstream (6010f358…)
infra/bots/tasks.json	Took upstream
tests/RegionTest.cpp, tests/SkRuntimeEffectTest.cpp	Took upstream

C API shim fixes (commit fabf585923)

kR16_float_SkColorType was inserted in the middle of the SkColorType C++ enum in m148
(between kA16_float and kRG16_float). This shifts all subsequent integer values by 1.

Changes:

• include/c/sk_types.h: Added R16_FLOAT_SK_COLORTYPE between A16_FLOAT_SK_COLORTYPE and R16G16_FLOAT_SK_COLORTYPE
• src/c/sk_enums.cpp: Added static_assert((int)SkColorType::kR16_float_SkColorType == (int)R16_FLOAT_SK_COLORTYPE, ...)

Items needing human attention

• SkFont.breakText() is fork-specific: This method exists only in our fork and must be preserved in every upstream merge. The conflict in include/core/SkFont.h was carefully resolved to keep our breakText() overloads alongside the new upstream makeStrikeRef() method.

• HarfBuzz pin: Our third_party/harfbuzz/BUILD.gn lists source files matching our pinned HarfBuzz 14.2.0. Upstream has a newer version with different source files. This MUST be kept as ours until HarfBuzz is separately bumped.

• DEPS strategy: We keep explicit pinned SHAs for security-critical dependencies (expat, libpng, zlib, harfbuzz, libjpeg-turbo, libwebp). These should only be updated in dedicated security/dependency-bump PRs, not in milestone syncs.

Created by skia-upstream-sync.

[mattleibow]

Closing this stale auto-generated skia-sync PR. The active milestone work is the m148 update (#4125 / #250); future milestones can be regenerated by the auto-sync workflow when needed.