Add priority field to processor tags

[HypeMC]

Continuation of #455.

Foo\Bar\Log\Processors\FirstProcessor:
    tags:
        - { name: monolog.processor, channel: http }

Foo\Bar\Log\Processors\SecondProcessor:
    tags:
        - { name: monolog.processor, channel: http, priority: -10 } # last

Foo\Bar\Log\Processors\ThirdProcessor:
    tags:
        - { name: monolog.processor, channel: http, priority: -20 } # very last

#[AsMonologProcessor(priority: -10)]
class SecondProcessor {}

#[AsMonologProcessor(priority: -20)]
class ThirdProcessor {}