Reorder non-sealed as one modifier

[abashev]

Brings over google/google-java-format#1107, a fix from google-java-format 1.23.

The bug

non-sealed private interface B extends I {} made the whole file fail with error: <identifier> expected. javac lexes non-sealed as three tokens, non, - and sealed, and ModifierOrderer looked at one token at a time: it never saw non-sealed, took the trailing sealed as the modifier to move in front of private, and left non- behind, so the reordered text no longer parsed.

From upstream, with the author kept

• Fix modifier order handling for non-sealed google/google-java-format#1107 by Liam Miller-Cushon, commit authored by them. The sorter reads the three tokens as one modifier (ModifierTokens) and writes it back whole. Adapted to this codebase's javax.annotation.Nullable and NullAway suppressions. The upstream golden Sealed and the sealedClass unit test come with it, with the expected output in this project's style.

Added here

• A second ModifierOrdererTest case for the exact shape that failed, non-sealed private.

Checked

• The golden and the new unit test fail on main and pass with the change.
• ./gradlew :open-java-format:test on JDK 21: 1503 tests, all green.
• The 15,747 files of the JDK 21 sources format exactly as before; none of them writes non-sealed out of JLS order.