Backingchain: add new case for event checking test

[meinaLi]

This PR adds: VIRT-294605 - Check events when doing blockcommit/blockpull/blockcopy

Test Result:

# avocado run --vt-type libvirt --test-runner=runner --vt-machine-type q35 backingchain.event_checking_event.commit_pull_copy
JOB ID     : 9d6548d466c9db166beb43f4d45d13a8278a30ef
JOB LOG    : /var/lib/avocado/job-results/job-2022-11-08T22.43-9d6548d/job.log
 (1/3) type_specific.io-github-autotest-libvirt.backingchain.event_checking_event.commit_pull_copy.blockcommit: PASS (67.47 s)
 (2/3) type_specific.io-github-autotest-libvirt.backingchain.event_checking_event.commit_pull_copy.blockpull: PASS (109.23 s)
 (3/3) type_specific.io-github-autotest-libvirt.backingchain.event_checking_event.commit_pull_copy.blockcopy: PASS (90.40 s)
RESULTS    : PASS 3 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 | CANCEL 0
JOB HTML   : /var/lib/avocado/job-results/job-2022-11-08T22.43-9d6548d/results.html
JOB TIME   : 269.88 s

Signed-off-by: Meina Li [email protected]

[meinaLi]

Label: modular_redesign

[nanli1]

Could we rename the folder name from event_checking_test to event_checking

[dzhengfy]

Could we rename the folder name from event_checking_test to event_checking I notice this name is aligning to the feature name in The structure of Polarion features google sheet. All feature names in column A are using 'test'. In my POV, this wording is redundant. So if we want to make the folder name shorter, we could remove it. But it is not a must to change to me because we already approved that google sheet content.