Cache the hasDecorator result in Jackson2Provider

 In Jackson2Provider there is line to check if there is @Decorator and @Decorators before write response.

This can be cached as what it does for JsonEndpointConfig to improve performance.   The benchmark test result shows the cache helps : 

----------------------Without cache ------------------------------------

wrk -c 30 -d 1m -t 30 -s  postLua http://localhost:8081/products/add

Running 1m test @ http://localhost:8081/products/add
30 threads and 30 connections
Thread Stats Avg Stdev Max +/- Stdev
Latency 657.36us 3.58ms 159.03ms 99.13%
Req/Sec 2.54k 519.46 11.11k 78.26%
4545572 requests in 1.00m, 498.52MB read
Requests/sec: 75627.27
Transfer/sec: 8.29MB

wrk -c 30 -d 1m -t 30 -s  postLua http://localhost:8081/products/add

Running 1m test @ http://localhost:8081/products/add
30 threads and 30 connections
Thread Stats Avg Stdev Max +/- Stdev
Latency 471.51us 1.00ms 75.33ms 97.08%
Req/Sec 2.62k 473.19 9.61k 78.33%
4688278 requests in 1.00m, 514.18MB read
Requests/sec: 78003.95
Transfer/sec: 8.55MB

---------------------With cache  ---------------------------------------

wrk -c 30 -d 1m -t 30 -s  postLua http://localhost:8081/products/add
Running 1m test @ http://localhost:8081/products/add
30 threads and 30 connections
Thread Stats Avg Stdev Max +/- Stdev
Latency 482.20us 1.93ms 130.01ms 98.88%
Req/Sec 2.68k 461.63 6.98k 79.64%
4810479 requests in 1.00m, 527.58MB read
Requests/sec: 80033.90
Transfer/sec: 8.78MB

wrk -c 30 -d 1m -t 30 -s  postLua http://localhost:8081/products/add
Running 1m test @ http://localhost:8081/products/add
30 threads and 30 connections
Thread Stats Avg Stdev Max +/- Stdev
Latency 441.03us 1.01ms 82.80ms 97.81%
Req/Sec 2.69k 421.98 5.65k 79.66%
4822241 requests in 1.00m, 528.87MB read
Requests/sec: 80229.33
Transfer/sec: 8.80MB