* Re-organized per 'state->var->func->effect->return' structure.
* Add "Hide Repost" button in channel page
Ticket: 1762
## Change
For the placement of the button, putting it inside the expanded settings group feels the most natural, plus we then don't need to check whether the channel has reposts or not before displaying it (the expanded area is for stuff like this).
## Notes
The tricky part was making the code maintainable w.r.t to the global "Hide Repost" setting. Changed `forceShowReposts` to `hideRepostsOverride`, hopefully makes things more obvious.
- undefined = fallback to global setting
- true/false = use override
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