Port convolve functions to SkOpts

This patch moves the C++/SSE2/NEON implementations of convolve functions
into the same place and uses SkOpts framework.
Also some indentation fix.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2500113004
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review-Url: https://codereview.chromium.org/2500113004
diff --git a/gn/opts.gni b/gn/opts.gni
index 2332de3..02a95cb 100644
--- a/gn/opts.gni
+++ b/gn/opts.gni
@@ -13,7 +13,7 @@
 ]
 
 armv7 = [
-  "$_src/opts/SkBitmapProcState_opts_arm.cpp",
+  "$_src/opts/SkBitmapProcState_opts_none.cpp",
   "$_src/opts/SkBlitMask_opts_arm.cpp",
   "$_src/opts/SkBlitRow_opts_arm.cpp",
 ]
@@ -28,7 +28,7 @@
 arm64 = [
   "$_src/opts/SkBitmapProcState_arm_neon.cpp",
   "$_src/opts/SkBitmapProcState_matrixProcs_neon.cpp",
-  "$_src/opts/SkBitmapProcState_opts_arm.cpp",
+  "$_src/opts/SkBitmapProcState_opts_none.cpp",
   "$_src/opts/SkBlitMask_opts_arm.cpp",
   "$_src/opts/SkBlitMask_opts_arm_neon.cpp",
   "$_src/opts/SkBlitRow_opts_arm.cpp",
@@ -44,7 +44,6 @@
 ]
 
 sse2 = [
-  "$_src/opts/SkBitmapFilter_opts_SSE2.cpp",
   "$_src/opts/SkBitmapProcState_opts_SSE2.cpp",
   "$_src/opts/SkBlitRow_opts_SSE2.cpp",
   "$_src/opts/opts_check_x86.cpp",