Better tiling for GEMMs. #4236

Job	Run time
build-and-test / bazel-linux-aarch64-gcc13	3m 6s
build-and-test / bazel-linux-aarch64-clang18	5m 34s
build-and-test / bazel-linux-x86_64-gcc-9	4m 30s
build-and-test / bazel-linux-x86_64-clang-18	6m 33s
build-and-test / cmake-android (arm64)	2m 40s
build-and-test / cmake-ios-arm64	2m 9s
build-and-test / cmake-ios-x86_64	3m 6s
build-and-test / cmake-android (armv7)	2m 41s
build-and-test / cmake-linux-aarch64	1m 26s
build-and-test / cmake-android (x86)	2m 50s
build-and-test / cmake-linux-armhf	1m 56s
build-and-test / cmake-linux-riscv64-rvv	2m 25s
build-and-test / cmake-linux-riscv64	5m 21s
build-and-test / cmake-linux-x86_64	1m 55s
build-and-test / cmake-macos-arm64	2m 20s
build-and-test / cmake-windows-x64	4m 56s
build-and-test / cmake-windows-x86	5m 29s
build-and-test / cmake-windows-arm64	4m 34s
	1h 3m 31s

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