tests: migrate demandimport.py away from deprecated `util` module symbols

tests/test-demandimport.py

@@ -58,12 +58,12 b' print("os =", f(os))'
 print("os.system =", f(os.system))
 print("os =", f(os))
 
-from mercurial import util
+from mercurial.utils import procutil
 
-print("util =", f(util))
-print("util.system =", f(util.system))
-print("util =", f(util))
-print("util.system =", f(util.system))
+print("procutil =", f(procutil))
+print("procutil.system =", f(procutil.system))
+print("procutil =", f(procutil))
+print("procutil.system =", f(procutil.system))
 
 from mercurial import hgweb
 print("hgweb =", f(hgweb))
@@ -100,6 +100,8 b' except ImportError as inst:'
     print('contextlib.unknownattr = ImportError: %s'
           % rsub(r"'", '', str(inst)))
 
+from mercurial import util
+
 # Unlike the import statement, __import__() function should not raise
 # ImportError even if fromlist has an unknown item
 # (see Python/import.c:import_module_level() and ensure_fromlist())

tests/test-demandimport.py.out

@@ -7,10 +7,10 b" errorproxy = <proxied module 'error'>"
 os = <unloaded module 'os'>
 os.system = <built-in function system>
 os = <module 'os' from '?'>
-util = <unloaded module 'util'>
-util.system = <function system at 0x?>
-util = <module 'mercurial.util' from '?'>
-util.system = <function system at 0x?>
+procutil = <unloaded module 'procutil'>
+procutil.system = <function system at 0x?>
+procutil = <module 'mercurial.utils.procutil' from '?'>
+procutil.system = <function system at 0x?>
 hgweb = <unloaded module 'hgweb'>
 hgweb_mod = <unloaded module 'hgweb_mod'>
 hgweb = <module 'mercurial.hgweb' from '?'>