tools: ynl: handle broken pipe gracefully in CLI

tools: ynl: handle broken pipe gracefully in CLI

When sending YNL CLI output into a pipe, closing the pipe causes a
BrokenPipeError. E.g. running the following and quitting less:

./tools/net/ynl/pyynl/cli.py --family rt-link --dump getlink | less
Traceback (most recent call last):
  File "/home/donaldh/net-next/./tools/net/ynl/pyynl/cli.py", line 160, in <module>
    main()
    ~~~~^^
  File "/home/donaldh/net-next/./tools/net/ynl/pyynl/cli.py", line 142, in main
    output(reply)
    ~~~~~~^^^^^^^
  File "/home/donaldh/net-next/./tools/net/ynl/pyynl/cli.py", line 97, in output
    pprint.PrettyPrinter().pprint(msg)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^
[...]
BrokenPipeError: [Errno 32] Broken pipe

Consolidate the try block for ops and notifications, and gracefully
handle the BrokenPipeError by adding an exception handler to the
consolidated try block.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250508112102.63539-1-donald.hunter@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>