[Feature] Working with php stubs

[zbigniew-malcherczyk-tg]

Describe the feature you'd like

This issue relates to #2931

Hello! Thank you for creating the stubs available in a single file. I checked it out and can bring some more input to improve the situation.

The ideal scenario for the phpstan is to have multiple stub files. It's not like I thought it would be best for the DX to have a single file. For some reason, phpstan is unable to process them all and it's getting stuck often using a tremendous amount of memory.

I would like to propose a couple of changes.

1. Keep all the stubs per class/interface stub file
2. Pack all the stub files as zip and keep them in release artefacts
3. Add documentation that would help use the stubs. That is

parameters:
    stubFiles:
        - vendor/datadog/dd-trace/src/ddtrace_php_ClassNameOne.stub.php
        - vendor/datadog/dd-trace/src/ddtrace_php_ClassNameThree.stub.php
        - vendor/datadog/dd-trace/src/ddtrace_php_ClassNameOne.stub.php

I believe a great example could the the phpstan symfony extension (https://github.com/phpstan/phpstan-symfony/tree/2.0.x/stubs)

Is your feature request related to a problem?

No response

Describe alternatives you've considered

No response

Additional context

No response