Update Shell API's method signatures and enable typedoc integration

[aalves08]

Summary

Fixes #15597
Fixes #15850

Important notice: needs a rebase from #15532 once that's merged

Occurred changes and/or fixed issues

• Update Shell API's methods usage signature to a pattern more "up-to-date" and easy to be consumed
• Integrate the Notification Center with the Shell API
• Add information for when the Shell API is available to be consumed
• Update typedoc integration to auto-generate new documentation (remove commented code so it's enabled by default)
• Remove growls from Shell API (deprecated)
• Add new System API to Shell API
• Fixes minor issues with focus trap on Shell API methods
• add unit tests for Shell API implementation

Technical notes summary

Areas or cases that should be tested

• Check if documentation looks and builds fine
• Check if all Shell API methods are working fine and display intellisense

Areas which could experience regressions

Screenshot/Video

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
• The PR has a Milestone
• The PR template has been filled out
• The PR has been self reviewed
• The PR has a reviewer assigned
• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes
• The PR has been reviewed in terms of Accessibility

[nwmac]

I think this is okay to get in - there are a few follow-ups to look at.

Need to work out between interfaces and types for some things. Some interfaces show up like EncryptedNotification that we probably don't want to see.

But, I'd suggest we get this in and iterate forward.