When looking at markers for a merged thread, the thread shown in the tooltip is always "Merged Thread"

[julienw]

STR:

1. Open this profile
2. Shift click some threads.
3. Hover some markers

=> notice that the displayed thread is always "Merged Thread". Instead we should show the originating thread.

Also the Thread line should probably come first rather than last.

┆Issue is synchronized with this Jira Task

[julienw]

I think the fix isn't obvious, and we might need to rearchitecture some things. So this is definitely not easy to do.