Add `buffer_size` to buffered log handlers

[homersimpsons]

Issue

Long running process might go out of memory (OOM) if buffered log handlers are filled

while (true) {
    $this->bufferedLogHandler->info('test');
}

fingers_crossed is buffer based so it can run into this issue.

Fix

A buffer_size should be append to the config. This settings will tell the handler to keep only the nth most recent messages so this will avoid OOM.

The configuration doc can be found there (permalink)

A value of 100 should be far enough.

[gulien]

In the production configuration, there is already a buffer size: https://github.com/thecodingmachine/symfony-nuxtjs/blob/master/src/api/config/packages/prod/monolog.yaml#L8