Fix/uncleared track meta on stop audio

[Neko-Life]

Changes in this PR

• Close dpp::discord_voice_client: track_meta is not cleared when stop_audio() is called #1124
• Avoid hardcoded size check
• Faster erase of outbuf when skipping marker
• Tested on Musicat -alpha, no problem so fat

Code change checklist

• I have ensured that all methods and functions are fully documented using doxygen style comments.
• My code follows the coding style guide.
• I tested that my change works before raising the PR.
• I have ensured that I did not break any existing API calls.
• I have not built my pull request using AI, a static analysis tool or similar without any human oversight.

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[Mishura4]

👍

[Mishura4]

👍 LGTM ship it

[Mishura4]

@Jaskowicz1