t/*: rearrange tests into numbered directories.

It was getting way too ad-hoc in there.  Let's reorganize the tests so that
there's a good, obvious, suggested sequence to run them in.

t/deps/dirtest/test.do

@@ -1,16 +0,0 @@
-rm -f log dir1/log dir1/stinky
-touch t1.do
-../../flush-cache
-redo t1
-touch t1.do
-../../flush-cache
-redo t1
-../../flush-cache
-redo-ifchange t1
-C1="$(wc -l <dir1/log)"
-C2="$(wc -l <log)"
-. ../../skip-if-minimal-do.sh
-if [ "$C1" -ne 1 -o "$C2" -ne 2 ]; then
-	echo "failed: t1>t1, c1=$C1, c2=$C2" >&2
-	exit 55
-fi