chore: String extension codestyle change

[JeneaVranceanu]

Summary of Changes

"Fixes" codestyle:

• fullNSRange is no longer a computed variable but a function fullNSRange();
• Changed the order of public, internal and default visibility functions in String+Extension.swift;
• Removed asciiValue extension from String and Character types as it's not used and is not public.

Test Data or Screenshots

None

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