Exclude Services tests from Linux JS Tests Job and Separate Workflow for flaky Selenium Tests

[RRosio]

Update: 06/03/22

• Originally, this PR attempted to pin jupyter_client <7.x to fix the services (macOS) Linux JS Tests job.
  However, while pinning jupyter_client <7.x allows the macOS services tests consistently pass locally, the CI test results are not consistent. That change has been discarded.

• Currently, the services (Ubuntu and macOS) tests are being excluded and are to be further addressed in a separate issue.

• Lastly, creating a separate workflow for flaky selenium tests

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Using jupyter_client 7.x dependency leads to different behavior.
The execution of the following code in a cell, results in only two of the four expected events

import os
from ipykernel.connect import get_connection_file
with open(get_connection_file(), 'w') as f:
       f.write('garbage')
       os._exit(1)

The two events trigged: 'kernel_restarting.Kernel', 'kernel_autorestarting.Kernel'
The two events not triggered: 'kernel_killed.Session', 'kernel_dead.Kernel'

[echarles]

Sounds like this PR does the job

Linux JS Tests / build (ubuntu, base) (pull_request) Successful in 3m
Flaky Selenium Tests / build (ubuntu, 3.8) (pull_request) Successful in 6m

@RRosio Is this ready for review?

[RRosio]

@echarles Yes please! Yes, this PR does those jobs! There are three builds tested under the Flaky Selenium Tests job, then the Selenium Tests job was modified to exclude those three builds that would be tested under the flaky workflow. Lastly the Linux JS Tests job was modified to exclude the services tests for both macOS and Ubuntu.
The three builds under Flaky Selenium Tests (ubuntu, 3.8),(macos, 3.7) and (macos, 3.9) are currently all passing too

[echarles]

LGTM. Thx @RRosio