[callstats] relocate the vpython imports

Recently the callstats runner started crashing due to scipy imports.

This CL moves the import to mitigate the crashes.

TBR=machenbach@chromium.org

Bug: v8:10269
Change-Id: I67c2093f12ae287354a59e9cd32b79c6288b8edd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2078571Reviewed-by: Tamer Tas <tmrts@chromium.org>
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Auto-Submit: Tamer Tas <tmrts@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66483}

tools/callstats.py

@@ -32,8 +32,6 @@ import operator
 from callstats_groups import RUNTIME_CALL_STATS_GROUPS
 
 import numpy
-import scipy
-import scipy.stats
 from math import sqrt
 
 
@@ -328,6 +326,10 @@ def do_run_replay_server(args):
 # Calculate statistics.
 
 def statistics(data):
+  # NOTE(V8:10269): imports moved here to mitigate the outage.
+  import scipy
+  import scipy.stats
+
   N = len(data)
   average = numpy.average(data)
   median = numpy.median(data)