fix(router): fix serializeQueryParams logic

[swseverance]

I am currently marking this as a breaking change out of an abundance of caution, because it does make a small change to the way query params are serialized into a url. The maintainers can decide if it truly is a breaking change.

corrects a bug that resulted in query params such as {a: 1, b:[]} being serialized as 'a=1&' instead of 'a=1'

resolves #42445

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?

It changes the way query params are serialized into a url

• 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?

Something like [queryParams]={a: 1, b:[]} gets serialized as 'a=1&'

Issue Number: #42445

What is the new behavior?

Something like [queryParams]={a: 1, b:[]} gets serialized as 'a=1'

Does this PR introduce a breaking change?

• Yes
• No

The url generated by the router link directive will be different if this PR is merged. It will no longer contain the extra ampersand.

Other information

[atscott]

Thanks for the fix! Depending on the presubmit results, we can probably submit this as purely a bug fix (without the breaking change). Will update once those tests have been run.

[AndrewKushnir]

@atscott FYI, I've started a global presubmit for the changes in this PR.

[atscott]

Global presubmits show no failures so we should be good to submit this as a non-breaking fix.

[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.}