chore: switch to Jest for unit tests

[brandonroberts]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[x] CI related changes
[ ] Documentation content changes
[x] Other... Please describe:

What is the current behavior?

Unit tests are run with a Jasmine runner

Closes #

What is the new behavior?

Unit tests and example app tests are run with Jest

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[alex-okrushko]

I'm not familiar with Jest - we cannot use jasmine.createSpyObj anymore?

[brandonroberts]

It's not supported by Jest without an additional third-party package.

[timdeschryver]

LGTM, I do have a questions tho.
Are we planning to run the tests with bazel in the future?
This won't cause problems with Jest, right?

[brandonroberts]

Yes, we will still run the tests with Bazel at some point, but they are too flakey in CI (probably due to memory constraints). This shouldn't cause issues with running the tests with Bazel in the future.