Improve startup speed of confluence by implementing an efficient CacheKey

Whilst profiling for PDFBox issues, I noticed that a lot of time was spent in String concatenation in org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.getCacheKey(),

I've overridden this class and am providing a memory efficient cacheKey that avoids String concatentation, on my machine this improves start up from ~46 secs to 37 secs