chore: Restructure test utilities into organized subdirectories

[github-actions]

Note

The pull request "chore: Restructure test utilities into organized subdirectories" was created by @philprime but did not reference an issue. Therefore this issue was created for better visibility in external tools like Linear.

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

Changes

SentryTestUtils

• Split into Headers/, Sources/, and SourcesCPP/ subdirectories
• Updated bridging header path to Headers/SentryTestUtils-ObjC-BridgingHeader.h

SentryTestUtilsDynamic

• Split into Headers/ and Sources/ subdirectories

SentryTestUtilsTests

• Split into Resources/ and Sources/ subdirectories
• Updated Info.plist path to Resources/Info.plist

Cleanup

• Removed references to non-existent files:
  • Brewfile-ci-test
  • SentryUIRedactBuilderTests+SpecialViews.swift
• Fixed SwiftLint function body length violation in Invocation.swift

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

#skip-changelog

[linear]

COCOA-890