Replace ical and office calendar image icons

[agh1]

Overview

This slices off one commit from #17259 for ease of review. I then added an improved way to display the icons and applied the same improvement in a parallel place.

This changes the icons on the bottom of the event info page to use Font Awesome. These are stacked icons, the left one showing a calendar with a download icon (to download a file for the one event), and the right one showing a calendar with a link (to subscribe to the calendar).

The original icon files were used nowhere else, so this removes them.

I also altered the Event Dashboard to use similar icons for similar things at the top. The four links (view a listing, subscribe to a RSS feed, download a calendar, link to a calendar feed) have always been difficult to differentiate with icons, so this should be helpful.

Before

After

Technical Details

Stacked Font Awesome icons don't always line up with non-stacked ones, so it's helpful that all of the icons together be stacked.

[civibot]

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[jaapjansma]

• General standards
  • Explain (r-explain)
    • PASS : The goal/problem/solution have been adequately explained in the PR.
  • User impact (r-user)
    • PASS: The change would be intuitive or unnoticeable for a majority of users who work with this feature.
  • Documentation (r-doc)
    • ISSUE: The developer documentation should be updated.
    • COMMENTS: We think it might be nice to also document the changes in this PR in the developer documentation.
  • Run it (r-run)
    • PASS: We checked in both dmaster and the test environment of this PR. We have checked the Dashboard of Events, the manage event screen and the public page of an event
    • ISSUE: We do think it might be worth to also replace the icons on the manage event screen
• Developer standards
  • Technical impact (r-tech)
    • PASS: The change preserves compatibility with existing callers/code/downstream.
  • Code quality (r-code)
    • PASS: The functionality, purpose, and style of the code seems clear+sensible.
  • Maintainability (r-maint)
    • PASS: The change sufficiently improves test coverage, or the change is trivial enough that it does not require tests.
  • Test results (r-test)
    • PASS: The test results are all-clear.

@agh could you also implement the icons on the manage event page?

[agh1]

@jaapjansma @mattwire I updated this to do the same thing on Manage Events as on the CiviEvent dashboard. Since it's a lot of repeated code, and it's weird that the URLs were all defined in Smarty, I created a new CRM_Event_BAO_Event::getICalLinks() function that supplies them.

[agh1]

I updated this with aria-hidden per #17318

[eileenmcnaughton]

test this please