[IMPROVEMENT] Fixes & support to Dynamic Type on all auth flow

[rafaelks]

@RocketChat/ios

This pull-request fixes issues caused by my changes on themes for #2348 and also add supports to Dynamic Type in all of the authentication flow.

Screenshots

[codecov]

Codecov Report

Merging #2349 into improvement/optimize_size_calculation will decrease coverage by 0.21%.
The diff coverage is 50%.

@@                            Coverage Diff                            @@
##           improvement/optimize_size_calculation    #2349      +/-   ##
=========================================================================
- Coverage                                  26.23%   26.02%   -0.22%     
=========================================================================
  Files                                        440      440              
  Lines                                      16437    16421      -16     
=========================================================================
- Hits                                        4313     4273      -40     
- Misses                                     12124    12148      +24

Impacted Files	Coverage Δ
Rocket.Chat/Theme/ThemeableViews.swift	44.17% <ø> (-13.11%)	⬇️
...Controllers/Auth/ConnectServerViewController.swift	58% <ø> (ø)	⬆️
...at/Controllers/Auth/LoginTableViewController.swift	0% <0%> (ø)	⬆️
...hat/Controllers/Auth/AuthTableViewController.swift	0% <0%> (ø)	⬆️
...t/Views/Cells/Auth/LoginServiceTableViewCell.swift	0% <0%> (ø)	⬆️
Rocket.Chat/Views/TextFields/StyledTextField.swift	97.56% <100%> (+0.5%)	⬆️
....Chat/Controllers/Auth/WelcomeViewController.swift	41.66% <100%> (-10.06%)	⬇️
Rocket.Chat/Views/Buttons/StyledButton.swift	66.03% <85.71%> (+0.65%)	⬆️
...xtensions/UITextField/UITextFieldClearButton.swift	0% <0%> (-100%)	⬇️
...ket.Chat/Views/Notification/NotificationView.swift	59.09% <0%> (-40.91%)	⬇️
... and 4 more

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[filipealva]

Looks good 👍