feat(timeline): consider unthreaded read receipts for ReceiptThread::Main timelines when computing timeline items states.

[stefanceriu]

This patch updates the Timeline Controller's handle_explicit_read_receipts method to also consider unthreaded read receipts on threaded main timelines when calculating timeline items states and adds a test for it.

This picks up from #5442 and fixes #5440

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.57%. Comparing base (a9ce1c6) to head (d8daecf).
⚠️ Report is 20 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5527      +/-   ##
==========================================
- Coverage   88.57%   88.57%   -0.01%     
==========================================
  Files         340      340              
  Lines       93694    93694              
  Branches    93694    93694              
==========================================
- Hits        82989    82988       -1     
- Misses       6573     6574       +1     
  Partials     4132     4132              

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[codspeed-hq]

CodSpeed Performance Report

Merging #5527 will not alter performance

_{Comparing unthreadedReadReceiptsOnThreadedClientsTheRevenge (d8daecf) with main (b3c53dd)}

Summary

✅ 31 untouched benchmarks

[bnjbvr]

Great job, thanks! Small proposal to change the test (or if you prefer, add a new one), and that shouldn't require any changes in the timeline's code, if I understand correctly

[bnjbvr]

I'm curious to propose a small change in this test, that I think wouldn't require a change in the rest of the code, in theory :)

Let's add a third event with id event_c, that's sent by Alice in a thread.

This event should be filtered out, because the timeline is set to hide_threaded_events.

Now, make Bob's read receipt point to event_c.

I think the outcome should remain the same, and the read receipt on event_b should be set to Bob's.

(This enhanced version proves that, even if the unthreaded read receipt is on an in-thread event, we can put it "at the right position" in the no-threaded-events timeline.)

[stefanceriu]

Great idea! Added it in 875ec25, fits right in 👍