Set hashicorp_key_management_cache_version_timeout to non-zero default

Right now hashicorp_key_management_cache_timeout has a default setting of 60 seconds, but hashicorp_key_management_cache_version_timeout has a default of zero, meaning no caching.

This leads to a lot of requests towards the Vault server and slows down operations significantly due to the network round trip wait times.

E.g. inserting significant amounts of rows into a table with "INSERT INTO ... SELECT ..." takes about four times as long with the current default as with the cache version timeout changed to 60 seconds.

The server will not really take immediate action upon seeing a new key version anyway, but will just start background re-encryption which can easily take more than a minute to complete, so a one minute cache timeout on key version checks should cause no issues at all, but will improve default performance quite significantly.