feat: automatically reload config after ddl change in a sharded cluster

[levkk]

Automatically trigger schema reload upon receiving applying DDL like CREATE TABLE or ALTER TABLE or DROP TABLE. N.B.: works on only single-node pgdog deployments - use for CI/staging only. #746

[codecov]

Codecov Report

❌ Patch coverage is 97.73371% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog/src/frontend/client/query_engine/query.rs	81.25%	3 Missing ⚠️
pgdog/src/frontend/router/parser/route.rs	70.00%	3 Missing ⚠️
...rc/frontend/client/query_engine/end_transaction.rs	0.00%	2 Missing ⚠️

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