feat: DDL/DML-only mirroring

[levkk]

Support mirroring DML or DDL only. DDL-only mirroring is helpful when maintaining long-running logical replicas. DML-only mirroring is helpful to simulate logical replication, without the replication aspect.

[[mirroring]]
source = "prod"
destination = "mirror"
level = "ddl"

This is helpful when resharding, for example, to make sure logical replication doesn't break. #807

[codecov]

Codecov Report

❌ Patch coverage is 82.68156% with 31 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog-config/src/core.rs	22.72%	17 Missing ⚠️
pgdog-config/src/replication.rs	12.50%	14 Missing ⚠️

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