[RojanFrancis]

Fixes C3 of #1330.

What's changed

SwitchCaseAssignmentsToSwitchExpression runs as part of UpgradeToJava21. It now leaves three shapes alone that it used to convert incorrectly, one commit each:

1. Labeled break (silent behaviour change):

   outer:
   for (int key : keys) {
       String formatted = "initialValue";
       switch (key) {
           case 1:
               formatted = "one";
               break outer;
           default:
               formatted = "other";
       }
       System.out.println(formatted);
   }

   This became String formatted = switch (key) { case 1 -> "one"; default -> "other"; };. It compiles, but the loop is no longer left, so later iterations now run. A labeled break is no longer treated as a plain end of case.

2. The selector reads the variable (doesn't compile): String s = "a"; switch (s) { case "a": s = "b"; .. } became String s = switch (s) {..}, which reads s before it is initialized.

3. Selector side effects reach the added default (silent behaviour change): int x = i; switch (i++) {..} without a default became int x = switch (i++) { .. default -> i; }, which reads the incremented i. The recipe now bails out when it would add a default, the initializer isn't a literal, and the selector may have side effects. A literal initializer is still converted (see convertWhenSelectorSideEffectsCannotReachLiteralDefault).

Is this the right change?

All three bail out instead of trying to rewrite, following the "prefer bailing out over guessing" guidance in #1330. For (3) I reused the recipe's existing canHaveSideEffects, so it's conservative: a non-literal initializer with a method-call selector and no default is now left as a statement. If that's too broad, it could be narrowed to "the selector writes a variable the initializer reads", but I didn't want to guess at aliasing through method calls.

The "comments in arrow blocks are lost" bullet (marked SUSPECTED) is not covered here.

Tests

The probe tests failed first: all three shapes were converted. They now pass, along with a positive test for the literal case. All 31 tests in SwitchCaseAssignmentsToSwitchExpressionTest pass.

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