Fixed various project warnings

[stefanceriu]

The purpose of this PR is to fix most project warnings so that we can start relying on them again without all the noise and also improve Xcode's handling of them and beach balling.
One of the biggest problems is that most warnings get duplicated between all the 4 targets.

Changes:

• increase swiftlint's warn limit for file lenght to 800. Error at 1000.
• added WARNING_CFLAGS -Wno-nullability-completeness and OTHER_SWIFT_FLAGS -Wno-nullability-completeness to both Project-Warnings.xcconfig and the Podfile
• Removed inaccesible ViewController from the main storyboard
• Fixed incorrect documentation parameters
• Fixed implicitly retaining self in blocks
• Replaced some intentional deprecations with comments
• Intentionally ignore deprecated declarations that have slim chances of getting fixed
• Completely ignore Flex wranings as the library is debug only
• Completely removed HPGrowingTextView as it's not necessary anymore

[github-actions]

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