Add a filesystem cache

Add a filesystem cache setting allow_dynamic_cache_resize, by default false, to allow dynamic resize of filesystem cache. Why: in certain environments (ClickHouse Cloud) all the scaling events happen through the restart of the process and we would love this feature to be explicitly disabled to have more control over the behaviour + as a safety measure. This PR is marked as backward incompatible, because in older versions dynamic cache resize worked by default without special setting. #79148 (Kseniia Sumarokova).