mie: refactor ir api into a separate sub-directory

mie/ir/convert/bitcode-write.c

@@ -0,0 +1,7 @@
+#include "convert.h"
+
+b_status write_value_to_bitcode(
+	struct mie_ir_converter *converter, struct mie_value *value)
+{
+	return B_ERR_NOT_SUPPORTED;
+}