[javac] some differences ecj <-> javac regarding 'recent' features

[stephan-herrmann]

While taking stock of run.javac test results regarding Java 23 I observed the following differences which might be within reach for resolution:

• PrimitiveInPatternsTestSH
  • 1 javac bug see https://mail.openjdk.org/pipermail/compiler-dev/2024-September/027729.html
• MarkdownCommentTest:
  • 1 error, javac not complaining about unresolvable @see reference
• ModuleCompilationTests
  • 4 errors
• PatternMatching16Test -- is this a structural problem?
  • 83 failures, obviously not suitable for running back-to-back with javac23
  • 67 errors vs javac16
• RecordPatternTest 3 errors, javac-generated code throws ArithmeticException instead of expected MatchException (see comments in tests):
  • testGH1977_instance_field()
  • testGH1977_static_field()
  • testIssue1985_2()
• SwitchExpressionsYieldTest
  • currently 175 failures, many of which due to ill-configured javac invocation
  • remaining: 17 failures
• SwitchPatternTest: 5 errors (some related to wrongly configured --enable-preview, others not yet analysed)
• SwitchPatternTest21: 2 errors
  * testInternalDomination_this() (ecj no error, javac 2 errors)
  * testNaming() // javac jdk21 allows components to be named, but they can't be referenced