Revert "Use the Conan package manager (#4367)"

This reverts commit c3a9f3dbf3.

Builds/CMake/deps/Findlz4.cmake

@@ -0,0 +1,24 @@
+find_package (PkgConfig)
+if (PKG_CONFIG_FOUND)
+  pkg_search_module (lz4_PC QUIET liblz4>=1.9)
+endif ()
+
+if(static)
+  set(LZ4_LIB liblz4.a)
+else()
+  set(LZ4_LIB lz4.so)
+endif()
+
+find_library (lz4
+  NAMES ${LZ4_LIB}
+  HINTS
+    ${lz4_PC_LIBDIR}
+    ${lz4_PC_LIBRARY_DIRS}
+  NO_DEFAULT_PATH)
+
+find_path (LZ4_INCLUDE_DIR
+  NAMES lz4.h
+  HINTS
+    ${lz4_PC_INCLUDEDIR}
+    ${lz4_PC_INCLUDEDIRS}
+  NO_DEFAULT_PATH)