Keep the initialization order in the MA0004 code fix

[meziantou]

Problem

The MA0004 code fix extracts the declaration of an await using statement so that ConfigureAwait can be appended to the variable:

await using (var a = expr) { }
// becomes
var a = expr;
await using (a.ConfigureAwait(false)) { }

TryInsertVariableStatementBeforeUsing walked up through the enclosing using (expr) statements to find a position where a statement could be inserted, then hoisted the declaration above all of them. That moves the initializer ahead of every crossed using expression:

using (Create("outer"))
await using (var resource = Create("inner")) { }

is fixed into

var resource = Create("inner");
using (Create("outer"))
await using (resource.ConfigureAwait(false)) { }

Create("inner") now runs before Create("outer"). It also breaks exception safety: if the hoisted initializer throws, the resources acquired by the crossed using statements are never disposed, whereas originally they were.

Change

The helper no longer ascends. It inserts the declaration only when it can go directly before the using statement itself (its parent is a block, a switch section, or the global statement list). When the using statement is the embedded statement of another statement, the fixer falls back to wrapping the declaration and the using statement in a block, which it already did for the other positions where a statement cannot be inserted:

using (Create("outer"))
{
    var resource = Create("inner");
    await using (resource.ConfigureAwait(false))
    {
    }
}

The generated block now carries Formatter.Annotation, so its body is reindented instead of keeping the indentation it had. That fallback path had no test coverage before, so the formatting had gone unnoticed.

Tests

• New regression test AwaitUsing_UnderUsingWithSideEffect_KeepsEvaluationOrder, with a side-effecting expression in the enclosing using and in the initializer.
• AwaitUsing_WithMultipleUsings_ShouldNotThrow expected the hoisted form, which is exactly the transformation that reorders the acquisition, so it now expects the block form.

MA0004 tests pass on all five Roslyn versions (35 each), and the full Roslyn 5.9 suite passes (4576 tests, 0 failed, 0 skipped). dotnet run --project src/DocumentationGenerator produces no markdown change.