Spring Don't get ContentCachingResponseWrapper in ShallowEtagHeaderFilter so that users can extend this wrapper

Issue Description: Code in ShallowEtagHeaderFilter: WebUtils.getNativeResponse(response, ContentCachingResponseWrapper.class); should be replaced into WebUtils.getNativeResponse(response, ConditionalContentCachingResponseWrapper.class); so that users can implement their own business logic based on ContentCachingResponseWrapper.

Change ContentCachingResponseWrapper to ConditionalContentCachingResponseWrapper so that it gets the right one.

private void updateResponse(HttpServletRequest request, HttpServletResponse response) throws IOException {

    ContentCachingResponseWrapper wrapper = 
// WebUtils.getNativeResponse(response, ContentCachingResponseWrapper.class);
   WebUtils.getNativeResponse(response, ConditionalContentCachingResponseWrapper.class);

        Assert.notNull(wrapper, "ContentCachingResponseWrapper not found");
        HttpServletResponse rawResponse = (HttpServletResponse) wrapper.getResponse();

        if (isEligibleForEtag(request, wrapper, wrapper.getStatus(), wrapper.getContentInputStream())) {
            String eTag = wrapper.getHeader(HttpHeaders.ETAG);
            if (!StringUtils.hasText(eTag)) {
                eTag = generateETagHeaderValue(wrapper.getContentInputStream(), this.writeWeakETag);
                rawResponse.setHeader(HttpHeaders.ETAG, eTag);
            }
            if (new ServletWebRequest(request, rawResponse).checkNotModified(eTag)) {
                return;
            }
        }

        wrapper.copyBodyToResponse();
    }

I have implemented my own Filter, and in my own Filter, i have implemented my own ResponseWrapper which extends ContentCachingResponseWrapper, everything works fine if ShallowEtagHeaderFilter is not loaded, but when it works with ShallowEtagHeaderFilter, when ShallowEtagHeaderFilter.updateResponse is invoked, the real HttpServletResponse get through WebUtils.getNativeResponse(response, ContentCachingResponseWrapper.class); become my own ResponseWrapper, so my own logic will be invoked inside ShallowEtagHeaderFilter, which is a mistake. By changing the code to WebUtils.getNativeResponse(response, ConditionalContentCachingResponseWrapper.class);, everything will be fine.

Affects: \<5.2.5.RELEASE and others>