No logs about empty state for tests with mocked store

[evgenyfedorenko]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https:/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?

This code adds an internal setting and a setter for mock store environment.
When set it suppresses the logs about the state which does not exist.

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

What is the current behavior?

Console warn logs numerous logs for mocked store which should not happen

Closes #2363

What is the new behavior?

Logs will be suppressed

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

This is a copy of #2420

[ngrxbot]

Preview docs changes for 88c5511 at https://previews.ngrx.io/pr2513-88c5511/

[timdeschryver]

LGTM