moved IO related code to stand-alone file, piped all read/and writes

through new API, /rad_log now can enable read and/or write logs with
"io", "io_reads", "io_writes" parameters.

src/linker/lnk_io.h

@@ -0,0 +1,9 @@
+#pragma once
+
+internal String8      lnk_read_data_from_file_path(Arena *arena, String8 path);
+internal String8Array lnk_read_data_from_file_path_parallel(TP_Context *tp, Arena *arena, String8Array path_arr);
+
+internal void lnk_write_data_list_to_file_path(String8 path, String8List list);
+internal void lnk_write_data_to_file_path(String8 path, String8 data);
+
+