Fix SyntaxWarning for '\w' '\d' in regexes

Use raw strings literals for the affected regexes

(venv-flent) $ flent -V
/path/to/flent/flent/metadata.py:247: SyntaxWarning: invalid escape sequence '\d'
  m = re.search("(qlen|txqueuelen) (\d+)", output)
/path/to/flent/flent/metadata.py:259: SyntaxWarning: invalid escape sequence '\w'
  m = re.search("Duplex: (\w+)", output)
Starting Flent 2.1.1+git.6c8dce50 using Python 3.12.4.
Flent v2.1.1+git.6c8dce50.
Running on Python 3.12.4 (main, Jun  9 2024, 22:05:49) [GCC 13.2.0].
No matplotlib found. Plots won't be available.
No usable Qt version found. GUI won't work.
ERROR: Missing test name.

flent/metadata.py

@@ -244,7 +244,7 @@ def get_link_params(iface):
         output = get_command_output("ifconfig %s" % iface)
 
     if output is not None:
-        m = re.search("(qlen|txqueuelen) (\d+)", output)
+        m = re.search(r"(qlen|txqueuelen) (\d+)", output)
         if m:
             link_params['qlen'] = m.group(2)
         m = re.search("ether ([0-9a-f:]{17})", output)
@@ -256,7 +256,7 @@ def get_link_params(iface):
         m = re.search("Speed: ([0-9]+Mb/s)", output)
         if m:
             link_params['speed'] = m.group(1)
-        m = re.search("Duplex: (\w+)", output)
+        m = re.search(r"Duplex: (\w+)", output)
         if m:
             link_params['duplex'] = m.group(1)