Documenting LogManager Setup and Best Practices

[lalitb]

Adding bit more guidance in our docs on setting up and managing loggers, especially since we've got those two paths: LOGMANAGER_INSTANCE for the straightforward cases and LogManagerProvider for when things get a bit more complex.

What's added?

• A breakdown of when and how to use LOGMANAGER_INSTANCE.
• A guide on leveraging LogManagerProvider for more advanced logging setups.
• Some advice on keeping things smooth and safe with loggers in multithreaded environments.
• Tips on choosing the right approach based on what you're building.

[lalitb]

@maxgolov @mkoscumb - whenever you have time to review this PR. Thanks.