feat: add InitializeSchema option to delayed requeuer publisher and subscriber configs

[AdrianZajkowski]

Motivation / Background

Currently, the delayed publisher/subscriber for both PostgreSQL and MySQL always attempts to automatically initialize the database schema (CREATE TABLE). This causes issues in production environments where the database user has restricted permissions and cannot create tables.
This change adds an InitializeSchema configuration option that allows users to disable automatic schema initialization when needed.

Details

Added InitializeSchema field to:

• DelayedMySQLPublisherConfig
• DelayedMySQLSubscriberConfig
• DelayedPostgreSQLPublisherConfig
• DelayedPostgreSQLSubscriberConfig
• DelayedRequeuerConfig

Changed hardcoded AutoInitializeSchema: true / InitializeSchema: true to use the config value instead
The option is propagated through the requeuer to its internal publisher and subscriber

Alternative approaches considered (if applicable)

Alternative approach could be to change name from InitializeSchema to DisableInitializeSchema to be backwards compatible if someone currently depends on auto initialize.

I used InitializeSchema to be consistent with naming in other files.

Checklist

The resources of our team are limited. There are a couple of things that you can do to help us merge your PR faster:

• I wrote tests for the changes.
• All tests are passing.
  • If you are testing a Pub/Sub, you can start Docker with make up.
  • You can start with make test_short for a quick check.
  • If you want to run all tests, use make test.
• Code has no breaking changes.
• (If applicable) documentation on watermill.io is updated.
  • Documentation is built in the github.com/ThreeDotsLabs/watermill/docs.
  • You can find development instructions in the DEVELOP.md.