fix(service-worker): clean up caches from old SW versions

[gkalpak]

PR Checklist

• 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

[x] Bugfix

What is the current behavior?

Installing a recent version of @angular/service-worker, leaves caches created by an old version (e.g. beta) behind. This can lead to exceeding the storage quota limitations imposed by browsers.

Issue Number: N/A

What is the new behavior?

On activate, the SW will schedule the removal of caches left behind by older versions. Since the SW immediately takes over all clients, it is safe to delete caches used by older (e.g. beta) @angular/service-worker versions to avoid running into browser storage quota limitations.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

[mary-poppins]

You can preview 1a42c3f at https://pr26319-1a42c3f.ngbuilds.io/.

[IgorMinar]

looks good! thanks

[ngbot]

I see that you just added the PR action: merge label, but the following checks are still failing:
     status "continuous-integration/travis-ci/pr" is failing

If you want your PR to be merged, it has to pass all the CI checks.

If you can't get the PR to a green state due to flakes or broken master, please try rebasing to master and/or restarting the CI job. If that fails and you believe that the issue is not due to your change, please contact the caretaker and ask for help.

[IgorMinar]

caretaker notes: ci flakes

[angular-automatic-lock-bot]

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