[IMPROVEMENT] Minor improvements to theming on RCVC

[Sameesunkaria]

@RocketChat/ios

• Add MessagesViewController as an observer for theming
• Use colors without transparency to improve performance
• Rename brightBlue to actionTintColor so that it matches the naming convention

[codecov]

Codecov Report

Merging #2268 into feature/integrate-rc-view-controller will increase coverage by 0.01%.
The diff coverage is 18.75%.

@@                           Coverage Diff                            @@
##           feature/integrate-rc-view-controller    #2268      +/-   ##
========================================================================
+ Coverage                                 25.61%   25.63%   +0.01%     
========================================================================
  Files                                       437      437              
  Lines                                     16507    16517      +10     
========================================================================
+ Hits                                       4229     4234       +5     
- Misses                                    12278    12283       +5

Impacted Files	Coverage Δ
...Views/Subscriptions/SubscriptionsSortingView.swift	0% <ø> (ø)	⬆️
...ket.Chat/Views/Subscriptions/ServersListView.swift	0% <ø> (ø)	⬆️
...ews/Chat/New Chat/Cells/BaseAudioMessageCell.swift	0% <0%> (ø)	⬆️
...hat/Views/Chat/New Chat/Cells/MessageURLCell.swift	0% <0%> (ø)	⬆️
...Views/Chat/New Chat/Cells/MessageActionsCell.swift	0% <0%> (ø)	⬆️
...ket.Chat/Views/Chat/New Chat/Cells/QuoteCell.swift	0% <0%> (ø)	⬆️
Rocket.Chat/Managers/MarkdownManager.swift	8.51% <0%> (ø)	⬆️
Rocket.Chat/Theme/ThemeableViews.swift	52.38% <0%> (-0.16%)	⬇️
...t/Views/Chat/New Chat/Cells/QuoteMessageCell.swift	0% <0%> (ø)	⬆️
Rocket.Chat/Theme/Theme.swift	95.45% <100%> (ø)	⬆️
... and 3 more

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[rafaelks]

Nice catch! :-)

[rafaelks]

Indeed a better name! 👍

[rafaelks]

Awesome, thank you @Sameesunkaria 🇮🇹!

[filipealva]

👍

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