(NFC) Expand test coverage for scheduled-reminders with {activity.*} tokens

[totten]

Overview

Expand test coverage for actionschedules with {activity.*} tokens.

This is extracted from @mattwire's branch in #16983.

Before

Less tests

After

More tests

Technical Details

Programming

[civibot]

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[eileenmcnaughton]

@totten does this test anything that is changed in any pr? (I mean it's generally good to test cover - just looking to understand if it adds tests to anything open pr related)

[totten]

@eileenmcnaughton In its original context, I believe the idea was: "This PR is changing the activity-tokens, so we should have more coverage for activity-tokens. Test-first/refactor-second". So, eg, one might have more confidence in a PR like #21088 with extra coverage.

[eileenmcnaughton]

Ok cool - it's probably a good starting point from which to make activity token coverage extensive