(bf) Remove unused ARRAY_BASE_OFFSET, ARRAY_INDEX_SCALE from read-only Heap Buffers

Two fields in Heap Buffers are unconditionally declared. But they are unused in read-only buffer classes.

    // Cached array base offset
    private static final long ARRAY_BASE_OFFSET = UNSAFE.arrayBaseOffset($type$[].class);

    // Cached array index scale
    private static final long ARRAY_INDEX_SCALE = UNSAFE.arrayIndexScale($type$[].class);

Affected classes: HeapByteBufferR, HeapCharBufferR, HeapDoubleBufferR, HeapFloatBufferR, HeapIntBufferR, HeapLongBufferR, HeapShortBufferR.

By widening '#if[rw]' we can remove redundant fields.