fix(vh): switch query mode to work on all networking backends

[JustinTArthur]

Description

Following Valheim's Call to Arms update in summer of 2025, Crossplay-enabled Valheim servers don't expose a Steamworks query port even when public. With this change, the config will default to session-only monitoring.

Power users can re-enable gamedig queries in their instance config if their server is public and not using Crossplay. A future change could be made to add first class support for a crossplay config variable and a check for it in fn_info_game_vh.

Fixes #4821

Type of change

• Bug fix (a change which fixes an issue).
• New feature (a change which adds functionality).
• New Server (new server added).
• Refactor (restructures existing code).
• Comment update (typo, spelling, explanation, examples, etc).

Checklist

PR will not be merged until all steps are complete.

• This pull request links to an issue.
• This pull request uses the develop branch as its base.
• This pull request subject follows the Conventional Commits standard.
• This code follows the style guidelines of this project.
• I have performed a self-review of my code.
• I have checked that this code is commented where required.
• I have provided a detailed enough description of this PR.
• I have checked if documentation needs updating.

Documentation

If documentation does need updating either update it by creating a PR (preferred) or request a documentation update.

• User docs: https://github.com/GameServerManagers/LinuxGSM-Docs
• Dev docs: https://github.com/GameServerManagers/LinuxGSM-Dev-Docs

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