[IMPROVEMENT] Change theme for MBProgressHUD

[rudrankriyam]

@RocketChat/ios

Closes #2577

Added the bezel.view = white, so that the view is visible in dark and black themes.

Before / After :

[codecov]

Codecov Report

Merging #2600 into develop will increase coverage by 0.68%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #2600      +/-   ##
===========================================
+ Coverage    25.99%   26.67%   +0.68%     
===========================================
  Files          463      456       -7     
  Lines        17203    16906     -297     
===========================================
+ Hits          4472     4510      +38     
+ Misses       12731    12396     -335

Impacted Files	Coverage Δ
Rocket.Chat/Theme/ThemeableViews.swift	52.63% <100%> (+10.17%)	⬆️
...ocket.Chat/Extensions/Models/ObjectExtension.swift	80% <0%> (-20%)	⬇️
...ontrollers/Base/Main/MainSplitViewController.swift	45% <0%> (-7.5%)	⬇️
...t/Views/Subscriptions/SubscriptionsTitleView.swift	12.5% <0%> (-4.17%)	⬇️
...Chat/Controllers/Chat/MessagesViewController.swift	31.49% <0%> (-2.76%)	⬇️
Rocket.Chat/Extensions/DateExtension.swift	64.28% <0%> (-2.39%)	⬇️
Rocket.Chat/Models/Subscription/Subscription.swift	47.61% <0%> (-1.27%)	⬇️
...ences/Profile/EditProfileTableViewController.swift	23.94% <0%> (-0.12%)	⬇️
...Chat/Models/Mapping/SubscriptionModelMapping.swift	87.71% <0%> (ø)	⬆️
Rocket.Chat/Models/User/User.swift	91.42% <0%> (ø)	⬆️
... and 35 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 43b49b6...711e313. Read the comment docs.

[rafaelks]

Looks good, thanks @snuff4!