bpo-34605, libregrtest: Rename --slaveargs to --worker-args (GH-9099)

Rename also run_tests_slave() to run_tests_worker().
diff --git a/Lib/test/libregrtest/cmdline.py b/Lib/test/libregrtest/cmdline.py
index dab17c3..bd126b3 100644
--- a/Lib/test/libregrtest/cmdline.py
+++ b/Lib/test/libregrtest/cmdline.py
@@ -170,7 +170,7 @@
     group.add_argument('--wait', action='store_true',
                        help='wait for user input, e.g., allow a debugger '
                             'to be attached')
-    group.add_argument('--slaveargs', metavar='ARGS')
+    group.add_argument('--worker-args', metavar='ARGS')
     group.add_argument('-S', '--start', metavar='START',
                        help='the name of the test at which to start.' +
                             more_details)
diff --git a/Lib/test/libregrtest/main.py b/Lib/test/libregrtest/main.py
index e262a7a..a176db5 100644
--- a/Lib/test/libregrtest/main.py
+++ b/Lib/test/libregrtest/main.py
@@ -542,9 +542,9 @@
                 print(msg, file=sys.stderr, flush=True)
                 sys.exit(2)
 
-        if self.ns.slaveargs is not None:
-            from test.libregrtest.runtest_mp import run_tests_slave
-            run_tests_slave(self.ns.slaveargs)
+        if self.ns.worker_args is not None:
+            from test.libregrtest.runtest_mp import run_tests_worker
+            run_tests_worker(self.ns.worker_args)
 
         if self.ns.wait:
             input("Press any key to continue...")
diff --git a/Lib/test/libregrtest/runtest_mp.py b/Lib/test/libregrtest/runtest_mp.py
index 907451c..1f07cfb 100644
--- a/Lib/test/libregrtest/runtest_mp.py
+++ b/Lib/test/libregrtest/runtest_mp.py
@@ -24,23 +24,23 @@
 
 
 def run_test_in_subprocess(testname, ns):
-    """Run the given test in a subprocess with --slaveargs.
+    """Run the given test in a subprocess with --worker-args.
 
     ns is the option Namespace parsed from command-line arguments. regrtest
-    is invoked in a subprocess with the --slaveargs argument; when the
+    is invoked in a subprocess with the --worker-args argument; when the
     subprocess exits, its return code, stdout and stderr are returned as a
     3-tuple.
     """
     from subprocess import Popen, PIPE
 
     ns_dict = vars(ns)
-    slaveargs = (ns_dict, testname)
-    slaveargs = json.dumps(slaveargs)
+    worker_args = (ns_dict, testname)
+    worker_args = json.dumps(worker_args)
 
     cmd = [sys.executable, *support.args_from_interpreter_flags(),
            '-u',    # Unbuffered stdout and stderr
            '-m', 'test.regrtest',
-           '--slaveargs', slaveargs]
+           '--worker-args', worker_args]
     if ns.pgo:
         cmd += ['--pgo']
 
@@ -58,8 +58,8 @@
     return retcode, stdout, stderr
 
 
-def run_tests_slave(slaveargs):
-    ns_dict, testname = json.loads(slaveargs)
+def run_tests_worker(worker_args):
+    ns_dict, testname = json.loads(worker_args)
     ns = types.SimpleNamespace(**ns_dict)
 
     setup_tests(ns)