Use osmocom.construct.{Bytes,GreedyBytes} for hexstring input support

The upstream construct.{Bytes,GreedyBytes} only support bytes/bytearray
input data for the encoder, while the [newly-created]
osmocom.construct.{Bytes,GreedyBytes} support alternatively hex-string input.

This is important in the context of encoding construct-based types from
JSON, where our osmocom.utils.JsonEncoder will automatically convert any
bytes to hex-string, while re-encoding those hex-strings will fail prior
to this patch.

Change-Id: I1c8df6350c68aa408ec96ff6cd1e405ceb1a4fbb
Closes: OS#6774

requirements.txt

@@ -5,7 +5,7 @@ cmd2>=1.5
 jsonpath-ng
 construct>=2.10.70
 bidict
-pyosmocom>=0.0.8
+pyosmocom>=0.0.9
 pyyaml>=5.1
 termcolor
 colorlog