delta-find: display more information about the search in some case

This will be useful to access the effect of the delta reuse policy.

tests/test-revlog-delta-find.t

@@ -329,8 +329,8 b' more subtle to test this behavior.'
   DBG-DELTAS: CHANGELOG: * (glob)
   DBG-DELTAS: MANIFESTLOG: * (glob)
   DBG-DELTAS: MANIFESTLOG: * (glob)
-  DBG-DELTAS: FILELOG:my-file.txt: rev=3: delta-base=2 * (glob)
-  DBG-DELTAS: FILELOG:my-file.txt: rev=4: delta-base=3 * (glob)
+  DBG-DELTAS: FILELOG:my-file.txt: rev=3: delta-base=2 is-cached=1 *search-rounds=1 try-count=1* (glob)
+  DBG-DELTAS: FILELOG:my-file.txt: rev=4: delta-base=3 is-cached=1 *search-rounds=1 try-count=1* (glob)
 
 Check that running "forced" on a non-general delta repository does not corrupt it
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