Use Queue in place of ArrayList when need to remove first element

There are couple of places where ArrayList is used a FIFO structure.
Using ArrayDeque would be more efficient.

src/jdk.compiler/share/classes/com/sun/tools/javac/api/JavacTaskPool.java
    private final Map<List<String>, List<ReusableContext>> options2Contexts;
(value type is in fact ArrayList)

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Analyzer.java
        Map<ClassSymbol, ArrayList<RewritingContext>> Q = new HashMap<>();