revset: changed minrev and maxrev implementations to use ordered sets

Performance Benchmarking:

0) max(tip:0)
1) min(0:tip)
2) min(0::)

b96cb15ec9e0 (2.9.1 release)

    0) ! wall 0.005699 comb 0.000000 user 0.000000 sys 0.000000 (best of 450)
    1) ! wall 0.005414 comb 0.010000 user 0.010000 sys 0.000000 (best of 493)
    2) ! wall 0.025951 comb 0.030000 user 0.030000 sys 0.000000 (best of 107)

05267e6e94dd (public tip at submission time)

    0) ! wall 0.015177 comb 0.020000 user 0.020000 sys 0.000000 (best of 175)
    1) ! wall 0.014779 comb 0.010000 user 0.010000 sys 0.000000 (best of 189)
    2) ! wall 12.345179 comb 12.350000 user 12.350000 sys 0.000000 (best of 3)

Current patches:

    0) ! wall 0.001911 comb 0.000000 user 0.000000 sys 0.000000 (best of 1357)
    1) ! wall 0.001943 comb 0.010000 user 0.010000 sys 0.000000 (best of 1406)
    2) ! wall 0.000405 comb 0.000000 user 0.000000 sys 0.000000 (best of 6761)

contrib/revsetbenchmarks.txt

@@ -3,3 +3,6 b' draft() and ::tip'
 roots(0::tip)
 author(lmoscovicz)
 author(lmoscovicz) or author(mpm)
+max(tip:0)
+min(0:tip)
+min(0::)

mercurial/revset.py

@@ -1035,7 +1035,7 b' def maxrev(repo, subset, x):'
     """
     os = getset(repo, spanset(repo), x)
     if os:
-        m = max(os)
+        m = os.max()
         if m in subset:
             return baseset([m])
     return baseset([])
@@ -1072,7 +1072,7 b' def minrev(repo, subset, x):'
     """
     os = getset(repo, spanset(repo), x)
     if os:
-        m = min(os)
+        m = os.min()
         if m in subset:
             return baseset([m])
     return baseset([])