MDEV-41080 startup code on Windows, remove checks for existing service

[vaintroub]

Summary

• Remove the is_existing_service heuristic; always attempt StartServiceCtrlDispatcher and fall back to running as a normal process if that fails
• Report unexpected errors from StartServiceCtrlDispatcher/RegisterServiceCtrlHandler to the Windows Event Log
• Use the authoritative service name returned as the first argument to svc_main by the Service Control Manager, instead of guessing it from the command line

🤖 Generated with Claude Code

[Copilot]

Copilot review overview

🟡 Changes recommended

The service dispatch table can prevent installed services from starting correctly.

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Review effort: Lite
Findings: 1

Open (1)

• Use NULL service name for single-service dispatcher entry · New

What changed in this PR

Updates Windows startup handling to use SCM dispatching, report errors, and rely on SCM-provided service names.

Changes:

• Removes service-existence heuristics.
• Adds Event Log reporting for startup errors.
• Uses the service name supplied by SCM.

File	Summary
sql/​winmain.cc	Critical issue: use NULL rather than an empty service name in the dispatch table. The file header also needs updating to reflect the new startup behavior.

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[Copilot]

Copilot review overview

🟡 Changes recommended

No-argument service invocations still bypass the service dispatcher and fail to connect to the SCM.

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Review effort: Balanced
Findings: 1

Open (1)

• Attempt SCM dispatch before mysqld_main on no-argument startup · New

Resolved since last review (1)

• Use NULL service name for single-service dispatcher entry

[sanja-byelkin]

Please remove magic number if possible otherwise it is good (as far as I can check :) )