stream-clone: disable gc for the entry listing section for the v2 format

This is similar to the change we did for the v3 format in 6e4c8366c5ce.

The benchmark bellow show this gives us a notable gains, especially on larger
repositories.

### benchmark.name                = hg.perf.stream-locked-section
  # benchmark.name                = hg.perf.stream-locked-section
  # bin-env-vars.hg.flavor        = default
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.version    = v2
 ## data-env-vars.name            = pypy-2018-08-01-zstd-sparse-revlog
5e931bf8707c: 0.503820  ~~~~~
1106d1bf695e: 0.470078   (-6.70%, -0.03)
 ## data-env-vars.name            = pypy-2024-03-22-zstd-sparse-revlog
5e931bf8707c: 0.535756  ~~~~~
1106d1bf695e: 0.490249   (-8.49%, -0.05)
 ## data-env-vars.name            = heptapod-public-2024-03-25-zstd-sparse-revlog
5e931bf8707c: 1.327041  ~~~~~
1106d1bf695e: 1.174636  (-11.48%, -0.15)
 ## data-env-vars.name            = netbeans-2018-08-01-zstd-sparse-revlog
5e931bf8707c: 2.439158  ~~~~~
1106d1bf695e: 2.220515   (-8.96%, -0.22)
 ## data-env-vars.name            = netbeans-2019-11-07-zstd-sparse-revlog
5e931bf8707c: 2.630794  ~~~~~
1106d1bf695e: 2.261473  (-14.04%, -0.37)
 ## data-env-vars.name            = mozilla-central-2018-08-01-zstd-sparse-revlog
5e931bf8707c: 5.769002  ~~~~~
1106d1bf695e: 5.062000  (-12.26%, -0.71)
 ## data-env-vars.name            = mozilla-try-2019-02-18-zstd-sparse-revlog
5e931bf8707c: 13.351750  ~~~~~
1106d1bf695e: 12.346655   (-7.53%, -1.01)
 ## data-env-vars.name            = mozilla-central-2024-03-22-zstd-sparse-revlog
5e931bf8707c: 10.772939  ~~~~~
1106d1bf695e: 9.495407  (-11.86%, -1.28)
 ## data-env-vars.name            = mozilla-unified-2024-03-22-zstd-sparse-revlog
5e931bf8707c: 10.864297  ~~~~~
1106d1bf695e: 9.475597  (-12.78%, -1.39)
 ## data-env-vars.name            = mozilla-try-2023-03-22-zstd-sparse-revlog
5e931bf8707c: 17.448335  ~~~~~
1106d1bf695e: 16.027474   (-8.14%, -1.42)

mercurial/streamclone.py

@@ -646,11 +646,12 b' def _emit2(repo, entries):'
 
     max_linkrev = len(repo)
     file_count = totalfilesize = 0
-    # record the expected size of every file
-    for k, vfs, e in entries:
-        for f in e.files():
-            file_count += 1
-            totalfilesize += f.file_size(vfs)
+    with util.nogc():
+        # record the expected size of every file
+        for k, vfs, e in entries:
+            for f in e.files():
+                file_count += 1
+                totalfilesize += f.file_size(vfs)
 
     progress = repo.ui.makeprogress(
         _(b'bundle'), total=totalfilesize, unit=_(b'bytes')