selftests: openvswitch: Fix escape chars in regexp.

Character sequences starting with `\` are interpreted by python as
escaped Unicode characters. However, they have other meaning in
regular expressions (e.g: "\d").

It seems Python >= 3.12 starts emitting a SyntaxWarning when these
escaped sequences are not recognized as valid Unicode characters.

An example of these warnings:

tools/testing/selftests/net/openvswitch/ovs-dpctl.py:505:
SyntaxWarning: invalid escape sequence '\d'

Fix all the warnings by flagging literals as raw strings.
Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Link: https://lore.kernel.org/r/20240416090913.2028475-1-amorenoz@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/openvswitch/ovs-dpctl.py

@@ -489,7 +489,7 @@ class ovsactions(nla):
                     actstr, reason = parse_extract_field(
                         actstr,
                         "drop(",
-                        "([0-9]+)",
+                        r"([0-9]+)",
                         lambda x: int(x, 0),
                         False,
                         None,
@@ -502,9 +502,9 @@ class ovsactions(nla):
                     actstr = actstr[len("drop"): ]
                     return (totallen - len(actstr))
 
-            elif parse_starts_block(actstr, "^(\d+)", False, True):
+            elif parse_starts_block(actstr, r"^(\d+)", False, True):
                 actstr, output = parse_extract_field(
-                    actstr, None, "(\d+)", lambda x: int(x), False, "0"
+                    actstr, None, r"(\d+)", lambda x: int(x), False, "0"
                 )
                 self["attrs"].append(["OVS_ACTION_ATTR_OUTPUT", output])
                 parsed = True
@@ -512,7 +512,7 @@ class ovsactions(nla):
                 actstr, recircid = parse_extract_field(
                     actstr,
                     "recirc(",
-                    "([0-9a-fA-Fx]+)",
+                    r"([0-9a-fA-Fx]+)",
                     lambda x: int(x, 0),
                     False,
                     0,
@@ -588,17 +588,17 @@ class ovsactions(nla):
                                 actstr = actstr[3:]
 
                             actstr, ip_block_min = parse_extract_field(
-                                actstr, "=", "([0-9a-fA-F\.]+)", str, False
+                                actstr, "=", r"([0-9a-fA-F\.]+)", str, False
                             )
                             actstr, ip_block_max = parse_extract_field(
-                                actstr, "-", "([0-9a-fA-F\.]+)", str, False
+                                actstr, "-", r"([0-9a-fA-F\.]+)", str, False
                             )
 
                             actstr, proto_min = parse_extract_field(
-                                actstr, ":", "(\d+)", int, False
+                                actstr, ":", r"(\d+)", int, False
                             )
                             actstr, proto_max = parse_extract_field(
-                                actstr, "-", "(\d+)", int, False
+                                actstr, "-", r"(\d+)", int, False
                             )
 
                             if t is not None: