several improvements for tests in Ubuntu 24.10

[hector-cao]

This MR comes as several commits, please check them out separately to have more context of all the changes.

The changes are:

• renaming of some test functions to be aligned with test file name
• increase ssh connection timeout for some stress tests since the guests can take more time to boot
• tox : add command to run all tests except performance ones
• does not make the test fail if we cannot stop the guest properly via monitor interface since for some tests, the guest may
  be shutdown already, etc ...
• for an unknown reason, we can not have multiple connections to the qemu process monitor interface via unix sock file
  only one connection is possible, others are blocked.
  for this reason, we will allow only one instance of monitor connection for each qemu process

[mckees]

I have the smallest of nitpicks, but other than that, LGTM