[mysql] general fixes

[heavycrystal]

1. MySQL connections were setting compression unconditionally, respect setting instead
2. remove unused Snowflake SQL
3. remove binlog/replication validation from peer creation so we can do initial load only mirrors for MySQL
4. make binlog/replication validation during mirror creation conditional on initial load only
5. change double quotes to backticks for statements we run on MySQL during initial load, brings us closer to supporting Vitess which can't handle ANSI_QUOTES

[Copilot]

Pull Request Overview

This PR implements several MySQL-related fixes and cleanups while also removing unused Snowflake SQL code. Key changes include conditionally setting compression for MySQL connections, revising replication connectivity checks to handle initial load only mirrors, and updating table quoting to backticks for improved Vitess support.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
flow/workflows/snapshot_flow.go	Updates table quoting logic based on peer database type to support Vitess
flow/connectors/snowflake/snowflake.go	Removes unused SQL constants for Snowflake
flow/connectors/mysql/validate.go	Adjusts replication connectivity checks and bypasses them when initial snapshot is used
flow/connectors/mysql/qrep.go	Improves partition query construction by using a parsed MySQL table identifier
flow/connectors/mysql/mysql.go	Makes setting the CLIENT_COMPRESS capability conditional on the compression configuration