Determine which kernel to use prior to notebook execution

[ptitzler]

Fixes #3134
See issue for details.

What changes were proposed in this pull request?

• Add and invoke new method find_best_kernel to replicate the behavior of the bootstrapper implementation for Kubeflow Pipelines.

How was this pull request tested?

• Added bootstrapper tests, which were already used to test the Kubeflow Pipelines bootstrapper

Developer's Certificate of Origin 1.1

   By making a contribution to this project, I certify that:

   (a) The contribution was created in whole or in part by me and I
       have the right to submit it under the Apache License 2.0; or

   (b) The contribution is based upon previous work that, to the best
       of my knowledge, is covered under an appropriate open source
       license and I have the right under that license to submit that
       work with modifications, whether created in whole or in part
       by me, under the same open source license (unless I am
       permitted to submit under a different license), as indicated
       in the file; or

   (c) The contribution was provided directly to me by some other
       person who certified (a), (b) or (c) and I have not modified
       it.

   (d) I understand and agree that this project and the contribution
       are public and that a record of the contribution (including all
       personal information I submit with it, including my sign-off) is
       maintained indefinitely and may be redistributed consistent with
       this project or the open source license(s) involved.

[kevin-bates]

Excellent - thank you for adding the tests as well!

[ptitzler]

Integration test failures are unrelated to the changes. They started to show up in yesterday's scheduled run.