fix: align timeout options with dmPython contract

[skhe]

What changed

• Match the official dmPython contract: login_timeout is milliseconds and defaults to 5000.
• Apply connection_timeout to SQL execution in seconds, including prepared and direct statements, instead of TCP dialing.
• Unblock canceled statements by closing the socket before driver cleanup.
• Add real-DM regressions for defaults, unresponsive login, locked updates and locked SELECT; verify a connection can query again after a timeout.
• Correct API documentation and the earlier test-results note.

Verification

• Real DM8 on local Orb: CPython 3.10, 125 passed; CPython 3.9, 3.11, 3.12, 3.13, 124 passed each before the final SELECT regression; the final SELECT regression passed separately on all four.
• Non-DM tests: 2 passed.
• Go bridge and vendored driver go test ./...: passed.
• Third-party patch consistency: passed.

Official behavior: https://eco.dameng.com/document/dm/zh-cn/pm/dmpython-interface and https://eco.dameng.com/document/dm/zh-cn/pm/dpi-rogramming-guide