Add GTID support for binlog streaming

[meiji163]

Description

This PR is a continuation of @timvaillancourt's PR #950 to add GTID support for streaming the binlog. Enable it with the --gtid flag. It requires gtid_mode=ON and enforce_gtid_consistency=ON, which is available in all MySQL versions supported by gh-ost.
Replacing file-based coordinates with GTID set coordinates is necessary for implementing migrations checkpoints and resumability in the future.

Details

• Add mysql.BinlogCoordinates interface, implemented by FileBinogCoordinates and GTIDBinlogCoordinates. GTID set operations are provided by go-mysql's replication package.
• In GTID mode, GoMySQLReader.currentCoordinates tracks the currently streaming transaction, while GoMySQLReader.LastTrxCoords tracks the last read transaction (similar to Retrieved_Gtid_Set).
• Update EventsStreamer.StreamEvents reconnection logic to use the LastTrxCoords. Surprisingly, the retry logic is currently unused because the go-mysql replication.BinlogSyncer has its own retry mechanism. My testing showed no problems with using the new reconnection logic, but I will not enable it now to keep this PR low risk.

Testing

All localtests pass with gtid mode (./script/docker-gh-ost-replica-tests run -g). Additionally, internal replica tests on production tables have been running for a day and revealed no data integrity issues.

In case this PR introduced Go code changes:

• contributed code is using same conventions as original code
• script/cibuild returns with no formatting errors, build errors or unit test errors.

[Copilot]

Pull Request Overview

This PR adds GTID (Global Transaction Identifier) support to gh-ost for streaming the binary log, which is necessary for implementing migration checkpoints and resumability. The main changes introduce a new --gtid flag that requires gtid_mode=ON and enforce_gtid_consistency=ON.

• Replaced file-based binlog coordinates with a BinlogCoordinates interface supporting both file and GTID coordinate types
• Updated reconnection logic to use last complete transaction coordinates for better reliability
• Added GTID validation and configuration checks

Reviewed Changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
go/mysql/binlog.go	Converted from struct to interface for coordinate abstraction
go/mysql/binlog_file.go	New file implementing file-based binlog coordinates
go/mysql/binlog_gtid.go	New file implementing GTID-based binlog coordinates
go/binlog/gomysql_reader.go	Updated to handle both coordinate types and track complete transactions
go/logic/streamer.go	Enhanced reconnection logic using last transaction coordinates
go/logic/inspect.go	Added GTID configuration validation
go/cmd/gh-ost/main.go	Added --gtid command line flag
localtests/test.sh	Added GTID test support and configuration

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