[core, ios, macos, android, node] Heatmap layer (#11046)

Co-Authored-By: Konstantin Käfer <mail@kkaefer.com>
Co-Authored-By: Anand Thakker <anandthakker@users.noreply.github.com>
Co-Authored-By: Minh Nguyễn <1ec5@users.noreply.github.com>

src/mbgl/programs/heatmap_program.cpp

@@ -0,0 +1,7 @@
+#include <mbgl/programs/heatmap_program.hpp>
+
+namespace mbgl {
+
+static_assert(sizeof(HeatmapLayoutVertex) == 4, "expected HeatmapLayoutVertex size");
+
+} // namespace mbgl