bpo-45850: Implement deep-freeze on Windows (#29648)

Implement changes to build with deep-frozen modules on Windows.
Note that we now require Python 3.10 as the "bootstrap" or "host" Python.
This causes a modest startup speed (around 7%) on Windows.

Tools/scripts/startuptime.py

@@ -0,0 +1,22 @@
+# Quick script to time startup for various binaries
+
+import subprocess
+import sys
+import time
+
+NREPS = 100
+
+
+def main():
+    binaries = sys.argv[1:]
+    for bin in binaries:
+        t0 = time.time()
+        for _ in range(NREPS):
+            result = subprocess.run([bin, "-c", "pass"])
+            result.check_returncode()
+        t1 = time.time()
+        print(f"{(t1-t0)/NREPS:6.3f} {bin}")
+
+
+if __name__ == "__main__":
+    main()