Use Vulkan rectangle lines to emulate OpenGL multisampled lines

SwiftShader recently added support for multisampled Bresenham lines to be spec
compliant with Vulkan, so now Angle must explicitly request non-Bresenham lines
when multisampling is enabled.

Bug: angleproject:4087
Change-Id: Ie854746144894e3e0a68622e985cbd4ba7781ac3
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1944529
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>

src/libANGLE/renderer/vulkan/vk_cache_utils.cpp

@@ -795,7 +795,8 @@ angle::Result GraphicsPipelineDesc::initializePipeline(
     VkPipelineRasterizationLineStateCreateInfoEXT rasterLineState = {};
     rasterLineState.sType = VK_STRUCTURE_TYPE_PIPELINE_RASTERIZATION_LINE_STATE_CREATE_INFO_EXT;
     // Always enable Bresenham line rasterization if available.
-    if (contextVk->getFeatures().bresenhamLineRasterization.enabled)
+    if (rasterAndMS.bits.rasterizationSamples <= 1 &&
+        contextVk->getFeatures().bresenhamLineRasterization.enabled)
     {
         rasterLineState.lineRasterizationMode = VK_LINE_RASTERIZATION_MODE_BRESENHAM_EXT;
         *pNextPtr                             = &rasterLineState;