Static error tester problem

[johnniwinther]

The test co19/LanguageFeatures/Parts-with-imports/export_A01_t02 fails to verify an error because the following line contains a comment.

The test has

  print(LibET);
//      ^^^^^
// [analyzer] unspecified
// [cfe] unspecified
  // From scope_lib2.dart
  print(libId); // Ok

and while an error reported for the CFE, the test fails with

static error failures:
- Wrong message at tests/co19/src/LanguageFeatures/Parts-with-imports/export_A01_t02.dart line 50, column 9: Undefined name 'LibET'.
  Expected: unspecified
From scope_lib2.dart

(indicating that the tester expects the comment in the following line to be part of the message).

If a line is inserted:

  print(LibET);
//      ^^^^^
// [analyzer] unspecified
// [cfe] unspecified

  // From scope_lib2.dart
  print(libId); // Ok

the test succeeds.

[munificent]

This was working as intended. But it apparently was never useful to support multi-line errors, so I went ahead and removed support for it: https://dart-review.googlesource.com/c/sdk/+/412185