Use a 1024 byte minimum weight for filter cache entries

This changes the weighing function for the filter cache to use a
configurable minimum weight for each filter cached. This value defaults
to 1kb and can be configured with the
`indices.cache.filter.minimum_entry_weight` setting.

This also fixes an issue with the filter cache where the concurrency
level of the cache was exposed as a setting, but not used in cache
construction.

Relates to #8268
There aren't any bad side-effects, without this, if the cache were closed and everything was invalidated, they would not be immediately removed, this just immediately removes them.