Refactor folder (#10475)

Move many third-party components' source codes from the src folder to a new folder called deps_src. The goal is to make the code structure clearer and easier to navigate.

deps_src/clipper/CMakeLists.txt

@@ -0,0 +1,19 @@
+cmake_minimum_required(VERSION 3.13)
+project(clipper)
+
+add_library(clipper STATIC
+# We are using ClipperLib compiled as part of the libslic3r project using Slic3r::Point as its base type.
+#    clipper.cpp
+#    clipper.hpp
+    clipper_z.cpp
+    clipper_z.hpp
+)
+
+target_include_directories(clipper PUBLIC
+    ${CMAKE_CURRENT_SOURCE_DIR}
+)
+
+target_link_libraries(clipper 
+    PUBLIC eigen
+    PRIVATE TBB::tbb TBB::tbbmalloc
+)