Fix animation glitch on 'this is the beginning of...' virtual event

[ara4n]

Use a stable id for TimelineStartRoomTimelineItem rather than creating a new UUID each time.

Fixes #4129

Pull Request Checklist

• I read the contributing guide.
• Pull request contains a changelog label.

UI changes have been tested with:

• iPhone and iPad simulators in portrait and landscape orientations.
• Dark mode enabled and disabled.
• Various sizes of dynamic type.
• Voiceover enabled.

[github-actions]

	Warnings
⚠️	You seem to have made changes to views. Please consider adding screenshots.

Generated by 🚫 Danger Swift against 743d3c0

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
1013	1	1012	0

View the full list of 1 ❄️ flaky tests

HomeScreenViewModelTests::testDeclineInvite()

Flake rate in main: 21.28% (Passed 37 times, Failed 10 times)

Stack Traces | 0.758s run time

XCTAssertEqual failed: ("["someAwesomeRoomId1", "someAwesomeRoomId2"]") is not equal to ("["someAwesomeRoomId2"]") (UnitTests/Sources/HomeScreenViewModelTests.swift:327)

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Velin92]

I think the only thing needed is to do TimelineItemIdentifier = .virtual(uniqueID: .init("TimelineStart")) or just "Start" and the rest should come by itself quite easily without any other change in any other file.

[Velin92]

No need to change anything else than TimelineStartRoomTimelineItem added a comment with the easiest and fastest solution