restart required always for any limit change?

[fluca1978]

While working on #329 I noted that the function restart_limit notifies that a restart is required pretty much everytime a single limit changes: https://github.com/agroal/pgagroal/blob/master/src/libpgagroal/configuration.c#L2843.
I think we could maybe relax a little this, for example, assuming the same limit entry, a restart could not be required if:

• e.max_size < n.max_size
  or
• e.min_size < n.min_size && n.min_size <= e.initial_size

that means we can handle increasing of the max_size, since we don't have (yet) connections and we can allow min_size to grow up to initial_size (if set).

This should be safe because pgagroal_reload_configuration calls a pass to pgagroal_validate_configuration, so in the case the limits have changed in a way that is not applicable, e.g., max_size greater than the total number of connections, the validation phase should catch it and a restart/reconfiguration would be required anyway.

[fluca1978]

Rethink a little about this, probably only the e.max_size < n.max_size could not trigger a restart, because for min_size it would be better to check about established connections, so it should be something like e.min_size < n.min_size && n.min_size < e.initial_size && n.min_size < current_connections.

In other words, it looks to me something it is not worth investing at this moment.