Enable reduceOpsTaskSplitting on select bots

This is a prep stage to get coverage of this option as we
move into Android code freeze.

This also removes the separate ReduceOpsTaskSplitting run from
the Pixel4XL. No need for it.

See skbug.com/10877#c27 for information.

Added this info to the Skia Gardener doc as advisory.

Bug: skia:10877
Change-Id: I69475f87b29aa125e285a8914015ac6a55e3390e
Cq-Include-Trybots: luci.skia.skia.primary:Test-Android-Clang-GalaxyS20-GPU-MaliG77-arm64-Debug-All-Android_Vulkan,Perf-Android-Clang-GalaxyS20-GPU-MaliG77-arm64-Release-All-Android_Vulkan_Skpbench,Test-Android-Clang-Nexus7-GPU-Tegra3-arm-Debug-All-Android,Perf-Android-Clang-Nexus7-GPU-Tegra3-arm-Release-All-Android,Perf-Android-Clang-Nexus5x-GPU-Adreno418-arm64-Release-All-Android,Test-Android-Clang-Nexus5x-GPU-Adreno418-arm64-Debug-All-Android,Test-Android-Clang-AndroidOne-GPU-Mali400MP2-arm-Debug-All-Android,Perf-Android-Clang-AndroidOne-GPU-Mali400MP2-arm-Release-All-Android
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/377856
Reviewed-by: Eric Boren <borenet@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Adlai Holler <adlai@google.com>
10 files changed