Alt-left/right sometimes doesn't switch through the TCOs in correct left-right order

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### Bug Summary
Alt-left and alt-right are supposed to switch to viewing the TCO on the left or right respectively. However, if the order of TCOs is changed after creation, then Alt-Left/Right switches between them left/right in the order they were initially placed in, instead of the order they are actually in. (This probably has something to do with how the absolute order of the TCOs in a file remains the same, even if the associated timestamps change.)

#### Steps to reproduce
1. Create two TCOs on a piano roll/automation clip, one after the other
2. Move the first TCO after the second
3. Open the TCO on the left and try hitting Alt-Left and Alt-Right.

#### Expected behavior
Alt-Right move to the next TCO, Alt-Left do nothing.

#### Actual behavior
Alt-Left moves to the TCO on the right, Alt-Right does nothing.

#### Screenshot
(Attached: video.)
https://user-images.githubusercontent.com/76674645/143668827-379834b6-e44d-454a-8244-8a7652f73e41.mp4
In the video, I have initially created them in order 1, 3, 2, then moved 3 after 2. Then I opened 1, and hit Alt-Right twice. It switches to 3 first, then 2. Then hitting Alt-Left twice switches to 3, then 1.
See: Attached file:
[TCO Alt-LeftRight.zip](https://github.com/LMMS/lmms/files/7611252/TCO.Alt-LeftRight.zip)

#### Affected LMMS versions

1.2.0, 1.3 (alpha)

Start by opening the attached TCO Alt-LeftRight.zip in LMMS and reproducing the Alt-Left/Alt-Right behavior after moving one TCO. Trace the keyboard navigation for TCOs and compare its ordering with their current left-to-right positions; done means navigation follows the current order in both directions and the reproduction no longer fails.

Written by the indexing model from the issue text.