fix(EventRecorder): Maintain focus for nodes besides input and textarea

[josephliccini]

In this change, the activeNode in Preboot is set for any focus event, not
just those in <input> or <textarea>.
This helps those who use screenreaders maintain focus during
the swap between server and client views.

Closes #105

• Please check if the PR fulfills these requirements

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

• What modules are related to this pull-request

• server side
• client side
• inline
• build process
• docs
• tests

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  remove unused proxy imports from some test files
  Bug fix

• What is the current behavior? (You can also link to an open issue here)
  Setting Focus is not applying to screenreader elements, only TextArea and Input elements #105

• What is the new behavior (if this is a feature change)?
  activeNode is set for focus on any element, not just input and textarea

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  No

• Other information:

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for all the commit author(s) or Co-authors. If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.
In order to pass this check, please resolve this problem and have the pull request author add another comment and the bot will run again. If the bot doesn't comment, it means it doesn't think anything has changed.

ℹ️ Googlers: Go here for more info.

[googlebot]

CLAs look good, thanks!

ℹ️ Googlers: Go here for more info.

[CaerusKaru]

LGTM

[CaerusKaru]

I can't cut a release this week, but if I don't cut one by Tuesday next week please ping this issue. And thank you for your contribution!