Allow disabling memory buffer increase for filesystem cache

Why it matters

This feature gives users control over the memory buffer sizing behavior for the filesystem cache, preventing automatic enlargement of buffer sizes. It is useful for optimizing memory usage and avoiding unexpected memory consumption growth in environments where buffer size increases are not desired.

How to use it

To use this feature, set the configuration option filesystem_cache_prefer_bigger_buffer_size to 0 (false) to disable automatic buffer size increase. This can be done in the server configuration file or via the SET query command.