feat(router-store): migration to add the default serializer

[timdeschryver]

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
[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?

Closes #

What is the new behavior?

This migration will add the default router serializer during the ng update migration if it isn't explicitly set already.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

This PR also adds a two utility functions (visitNgModuleImports and containsProperty)schematics-core.

[ngrxbot]

Preview docs changes for aacd0e9 at https://previews.ngrx.io/pr2291-aacd0e9/