[FIX] Reintroduce message drafting

[cardoso]

@RocketChat/ios

Also moved some extensions to other files to keep MessageViewController.swift under 400 lines.

Closes #2302

[codecov]

Codecov Report

Merging #2308 into develop will increase coverage by 0.25%.
The diff coverage is 39.65%.

@@             Coverage Diff             @@
##           develop    #2308      +/-   ##
===========================================
+ Coverage    26.02%   26.27%   +0.25%     
===========================================
  Files          433      436       +3     
  Lines        15875    15918      +43     
===========================================
+ Hits          4132     4183      +51     
+ Misses       11743    11735       -8

Impacted Files	Coverage Δ
...ntrollers/Chat/MessagesViewControllerSending.swift	0% <0%> (ø)	⬆️
...Chat/Controllers/Chat/MessagesViewController.swift	33.51% <100%> (-0.33%)	⬇️
...rollers/Chat/MessageViewControllerEmptyState.swift	19.04% <19.04%> (ø)
...trollers/Chat/MessageViewControllerSearching.swift	36.36% <36.36%> (ø)
...trollers/Chat/MessagesViewControllerDrafting.swift	75% <75%> (ø)
...ontrollers/Base/Main/MainSplitViewController.swift	45% <0%> (-7.5%)	⬇️
... and 5 more

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[filipealva]

The changes are looking good overall! 💯 I found only one issue, after sending the message we are not cleaning the draft for a channel/group/dm. So you send it but if you close and open the channel again the message you just sent will still be there:

[cardoso]

Nice catch @filipealva . Thank you. Fixed it.

[filipealva]

Awesome!!! 💯