tests: add tests of debugmergestate with unresolved/resolved path conflicts

I'm about to change `hg debugmergestate` and it broke on these "pu"
and "pr" records on my first attempt (D8113), so let's add test
coverage.

Differential Revision: https://phab.mercurial-scm.org/D8119

tests/test-pathconflicts-merge.t

@@ -75,6 +75,14 b' Merge - local file conflicts with remote'
   M a/b/c/d
   A a/b~0ed027b96f31
   R a/b
+  $ hg debugmergestate
+  * version 2 records
+  local: 0ed027b96f31a2560c8abe689ba59876409a2b8e
+  other: 9049d9534d5c5d16264aab02b4b9e20d03faabef
+  labels:
+    local: working copy
+    other: merge rev
+  unrecognized entry: P	a/b	pu	a/b~0ed027b96f31	l
   $ hg resolve --all
   a/b: path conflict must be resolved manually
   $ hg forget a/b~0ed027b96f31 && rm a/b~0ed027b96f31
@@ -106,6 +114,14 b' Merge - local symlink conflicts with rem'
   $ hg mv a/b~2ea68033e3be a/b.old
   $ hg resolve --mark a/b
   (no more unresolved files)
+  $ hg debugmergestate
+  * version 2 records
+  local: 2ea68033e3be03a560471c1fc9e5704fbedb9b4b
+  other: 9049d9534d5c5d16264aab02b4b9e20d03faabef
+  labels:
+    local: working copy
+    other: merge rev
+  unrecognized entry: P	a/b	pr	a/b~2ea68033e3be	l
   $ hg resolve --list
   R a/b
   $ hg commit -m "merge link and dir (renamed link)"