tests/bench: Add tests for various ways to pass function args.

Passing 3 args with keywords is for example 50% slower than via positional
args.

tests/bench/func_args-1.1-pos_1.py

+import bench
+
+def func(a):
+    pass
+
+def test(num):
+    for i in iter(range(num)):
+        func(i)
+
+bench.run(test)

tests/bench/func_args-1.2-pos_3.py

+import bench
+
+def func(a, b, c):
+    pass
+
+def test(num):
+    for i in iter(range(num)):
+        func(i, i, i)
+
+bench.run(test)

tests/bench/func_args-2-pos_default_2_of_3.py

+import bench
+
+def func(a, b=1, c=2):
+    pass
+
+def test(num):
+    for i in iter(range(num)):
+        func(i)
+
+bench.run(test)

tests/bench/func_args-3.1-kw_1.py

+import bench
+
+def func(a):
+    pass
+
+def test(num):
+    for i in iter(range(num)):
+        func(a=i)
+
+bench.run(test)

tests/bench/func_args-3.2-kw_3.py

+import bench
+
+def func(a, b, c):
+    pass
+
+def test(num):
+    for i in iter(range(num)):
+        func(c=i, b=i, a=i)
+
+bench.run(test)