[5.7] Lenient log stacks

[Propaganistas]

A simple yet powerful addition to the stack log driver: whenever a log stack is marked as lenient, the stack gets wrapped in the WhatFailureGroupHandler. Taken from Monolog's documentation:

This handler extends the GroupHandler ignoring exceptions raised by each child handler. This allows you to ignore issues where a remote tcp connection may have died but you do not want your entire application to crash and may wish to continue to log to other handlers.

So in this case log handlers throwing exceptions themselves are gracefully ignored, allowing the stack to continue. Highly useful to prevent white screens in production when for instance Slack cannot be reached.

I had a hard time choosing the right keyword (lenient, tolerant, continue, ignore_exceptions, ...), so please adjust as desired.

Disclaimer: I know this can be accomplished by tapping into the Monolog instance (tap) and rebinding the handler, but since it is such a useful thing I figured suggesting it as a config would be appropriate and helpful to many that are unaware of the possibility.

[taylorotwell]

Lol... that's a great class name from Monolog :)

[taylorotwell]

Renamed option to ignore_exceptions.