Wrong error message when using chunks cache with memcached

[yeya24]

Describe the bug
I am trying to configure memcached as chunks cache backend but I didn't provide memcached address. I got the following error message, which is wrong as it says index cache backend address not chunks cache. We can maybe just make it generic to be memcached backend address. I believe we have the same issue when using redis as backend

error validating config: invalid TSDB config: chunks-cache configuration: no index cache backend addresses