Fold conv package into fmt

Both packages had nearly identical dependency requirements, so merging
them should help reduce the complexity of the build graph.

tool/build/lib/dis.c

@@ -20,9 +20,9 @@
 #include "libc/alg/alg.h"
 #include "libc/alg/arraylist2.internal.h"
 #include "libc/bits/safemacros.internal.h"
-#include "libc/conv/itoa.h"
 #include "libc/fmt/bing.internal.h"
 #include "libc/fmt/fmt.h"
+#include "libc/fmt/itoa.h"
 #include "libc/log/check.h"
 #include "libc/log/log.h"
 #include "libc/macros.h"