fix(router): better ngZone checking for warning

[trotyl]

Closes #25837

PR Checklist

Please check if your PR fulfills the following requirements:

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

PR Type

What kind of change does this PR introduce?

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

What is the current behavior?

Issue Number: #25837

NgZone.isInAngularZone() results to false in testing, and cause warning.

What is the new behavior?

Checking NgZone.isInAngularZone() when constructing Router, considering NgZone not enabled when result being false.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[atscott]

@JiaLiPassion Can you review this PR?

[JiaLiPassion]

@atscott , sure, I will check this one.

[atscott]

LGTM. Adding my approval and marking as ready for merge, pending presubmit results.

@JiaLiPassion - please let me know if you notice anything particularly alarming about this change. It seems reasonable to me and at this point I'm in favor of the "merge and see what happens" strategy if we can't make a definitive decision one way or another; this is only a dev-mode warning that wouldn't affect production applications but does appear to cause a lot of friction in tests as it is.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}