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/fast_float/CMakeLists.txt

@@ -0,0 +1,15 @@
+cmake_minimum_required(VERSION 3.13)
+project(fast_float)
+
+add_library(fast_float INTERFACE)
+
+target_include_directories(fast_float INTERFACE
+    ${CMAKE_CURRENT_SOURCE_DIR}
+)
+
+target_sources(fast_float INTERFACE
+    ${CMAKE_CURRENT_SOURCE_DIR}/fast_float.h
+)
+
+# Require C++14 for fast_float
+target_compile_features(fast_float INTERFACE cxx_std_14)