chore: Restructure test utilities into organized subdirectories (#6639)

Reorganizes SentryTestUtils, SentryTestUtilsDynamic, and SentryTestUtilsTests
into clearer subdirectory structures in preparation for adopting xcodegen.

Changes:
- SentryTestUtils: Split into Headers/, Sources/, and SourcesCPP/
- SentryTestUtilsDynamic: Split into Headers/ and Sources/
- SentryTestUtilsTests: Split into Resources/ and Sources/
- Updated bridging header and Info.plist paths accordingly
- Removed references to non-existent files (Brewfile-ci-test, SentryUIRedactBuilderTests+SpecialViews.swift)
- Fixed SwiftLint violation in Invocation.swift

This improves code organization and makes the project structure more consistent
before transitioning to xcodegen for project file management.

Author: philprime

Sentry.xcodeproj/project.pbxproj

@@ -48,6 +48,7 @@ class Invocation: Loggable {
         try initialize()
     }
 
+    // swiftlint:disable:next function_body_length
     private func initialize() throws {
         /// `NSMethodSignature *methodSignature = [target methodSignatureForSelector: selector]`
         let methodSignature: NSObject