revlog: remove legacy usage of `_sparserevlog`

revlog: remove legacy usage of `_sparserevlog`

All core code is now getting the setting from the DeltaConfig object.

--- a/mercurial/revlog.py	Tue Oct 10 11:24:37 2023 +0200
+++ b/mercurial/revlog.py	Tue Oct 10 11:27:39 2023 +0200
@@ -2077,7 +2077,7 @@
 
     def issnapshot(self, rev):
         """tells whether rev is a snapshot"""
-        if not self._sparserevlog:
+        if not self.delta_config.sparse_revlog:
             return self.deltaparent(rev) == nullrev
         elif hasattr(self.index, 'issnapshot'):
             # directly assign the method to cache the testing and access

--- a/mercurial/revlogutils/deltas.py	Tue Oct 10 11:24:37 2023 +0200
+++ b/mercurial/revlogutils/deltas.py	Tue Oct 10 11:27:39 2023 +0200
@@ -622,7 +622,7 @@
     #   possible to build pathological revlog where delta pattern would lead
     #   to too many reads. However, they do not happen in practice at all. So
     #   we skip the span check entirely.
-    if not revlog._sparserevlog and maxdist < deltainfo.distance:
+    if not revlog.delta_config.sparse_revlog and maxdist < deltainfo.distance:
         return False
 
     # Bad delta from new delta size:
@@ -715,7 +715,7 @@
 
     deltalength = revlog.length
     deltaparent = revlog.deltaparent
-    sparse = revlog._sparserevlog
+    sparse = revlog.delta_config.sparse_revlog
     good = None
 
     deltas_limit = textlen * LIMIT_DELTA2TEXT
@@ -875,7 +875,7 @@
             break
 
     # If sparse revlog is enabled, we can try to refine the available deltas
-    if not revlog._sparserevlog:
+    if not revlog.delta_config.sparse_revlog:
         yield None
         return
 
@@ -916,7 +916,7 @@
     # Why search for delta base if we cannot use a delta base ?
     assert revlog.delta_config.general_delta
     # also see issue6056
-    sparse = revlog._sparserevlog
+    sparse = revlog.delta_config.sparse_revlog
     curr = len(revlog)
     prev = curr - 1
     deltachain = lambda rev: revlog._deltachain(rev)[0]
@@ -1158,9 +1158,9 @@
                 raise error.ProgrammingError(msg)
             deltabase = chainbase
         snapshotdepth = None
-        if revlog._sparserevlog and deltabase == nullrev:
+        if revlog.delta_config.sparse_revlog and deltabase == nullrev:
             snapshotdepth = 0
-        elif revlog._sparserevlog and revlog.issnapshot(deltabase):
+        elif revlog.delta_config.sparse_revlog and revlog.issnapshot(deltabase):
             # A delta chain should always be one full snapshot,
             # zero or more semi-snapshots, and zero or more deltas
             p1, p2 = revlog.rev(revinfo.p1), revlog.rev(revinfo.p2)