Add support for storage.enable-ttl to tikv config

[GeertJohan]

Feature Request

I would like to run tikv (without tidb) with ttl enabled. This is a feature in tikv, but the configuration value to enable it is missing in the tidb-operator manifest structures, and therefore not passed on to tikv.

I am able to work on this feature. But would like to discuss implementation details with the tidb-operator team. A naïve implementation would just pass the configuration value, however, the big warning on the enable-ttl documentation shows that it should not be used for tidb clusters. So I suspect we would want to have some check that denies manifests with enable-ttl=true while tidb is also enabled?