Start a switch expression on the line of the declaration it initializes

[abashev]

Closes #63. Brings over palantir#1789 by Patrick Koenig, which fixes palantir#1258 and shipped in palantir-java-format 2.99.0.

What changes

A local variable or a field initialized with a switch expression broke after the =, with the switch indented by eight, while a plain assignment of the same switch already kept it on the line:

// before
        int x =
                switch (y) {
                    case 1 -> 1;
                    default -> throw new IllegalStateException();
                };

// after, the same shape as `x = switch (y) {` had all along
        int x = switch (y) {
            case 1 -> 1;
            default -> throw new IllegalStateException();
        };

From upstream, with the author kept

• Don't break line when switch expression used in declaration assignment palantir/palantir-java-format#1789 by Patrick Koenig, cherry-picked as it is (git cherry-pick -x, rename detection mapped palantir-java-format/ to open-java-format/, nothing to adapt). declareOne loses its special case for an initializer that starts with switch, so the initializer takes the same level as any other, and visitCase drops the forced break after a rule case's ;. The golden ExpressionSwitch moves in the same two methods as upstream's.

Added here

• The upstream commit rewrote the input of test1 into the new shape, so both declarations in the golden started from the target form and nothing checked the move itself. test1's input goes back to the old shape, =, a line break and the switch, with the same expected output; a field initialized with a switch expression, written in the same old shape, is added too, since no golden covered a field. Both fail on main.

Checked

• The golden fails on main and passes with the change: assignment and the upstream test1 output pin the new shape, the restored test1 input and the new field pin the move from the old one.
• ./gradlew :open-java-format:test on JDK 21: 1497 tests, all green.
• Of the 15,747 files of the JDK 21 sources, 51 format differently: the 57 declarations initialized with a switch expression that Bring over upstream PR #1789: start a switch expression on the line of the declaration it initializes #63 counted, every one of them. The switch moves onto the = line and its body eight columns left; in 9 of the files a case body or a throw argument that had to wrap at the deeper indent now fits on one line. Nothing else changes.
• The new output is stable on a second run, apart from MethodHandleImpl.java and Calendar.java, which change on a second run on main already, in the same way (a trailing comment after a call, and a block comment before a case).

Version

This changes the output of files that format correctly today, which the README reserves for 3.0 (#22 and #31 are in the same position). Merging is the call on that, not this PR.