Adding Apm + options to enable it.

[sambar-delen]

Hi, I'm using EasyCaching.Redis in one of my projects. I'm trying to debug something using APM so I thought it would be handy to add it in. This is the first time I ever contribute anything. I'm not familiar with the structure of the repo and how to test is, but if I look at the APM docs, this should be enough. If there is anything I'm missing, please let me know. Thanks for your time.

closes #461