common: move download functions to download.(cpp|h) (#17059)

* common: move download functions to download.(cpp|h)

* rm unused includes

* minor cleanup

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Co-authored-by: Georgi Gerganov <[email protected]>

Author: ngxson

common/CMakeLists.txt

@@ -56,6 +56,8 @@ add_library(${TARGET} STATIC
     common.h
     console.cpp
     console.h
+    download.cpp
+    download.h
     http.h
     json-partial.cpp
     json-partial.h