fix(common): check for invalid markers

[srl295]

• pattern parser update
• correct spelling of Error_InvalidVariableIdentifier
• track and report bad marker strings (look like markers but not)
• fix: may have missed markers mentioned in variables
• tests for above

Fixes: #12467

@keymanapp-test-bot skip

[keymanapp-test-bot[bot]]

User Test Results

Test specification and instructions

User tests are not required

Test Artifacts

• Android
  • Keyman for Android apk
  • FirstVoices for Android 16.0 apk
  • FirstVoices Keyboards for Android apk
  • KeyboardHarness apk
  • Keyman for Android 16.0 apk
  • KMSample1 apk
  • KMSample2 apk
• Developer
  • Keyman Developer - build pending
  • Compiler Regression Tests - build pending
  • kmcomp.zip - build pending
• iOS
  • Keyman for iOS (simulator image)
  • FirstVoices Keyboards for iOS (simulator image)
  • TestFlight internal PR build version - 18.0.134 (0.12613.12242)
• Keyboards
  • Test Keyboards - build pending
• Web
  • KeymanWeb Test Home
• Windows
  • Keyman for Windows - build pending
  • FirstVoices Keyboards for Windows - build pending
  • Text Editor (32 bit) - build pending
  • Text Editor (64 bit) - build pending

[keyman-server]

Changes in this pull request will be available for download in Keyman version 18.0.138-alpha