void clear() {
            this.bytes = 0;
            this.pos = this.offset = 0;
            Arrays.fill(this.elements, null);
        }
A recyclable segment.
@author boyan(boyan@antfin.com)

@param <T>
jraft-core/src/main/java/com/alipay/sofa/jraft/util/SegmentList.java