net/turnserver: Update 4.6.3 => 4.10.0 (fix 3 CVEs)

Changelogs:
https://github.com/coturn/coturn/blob/4.10.0/ChangeLog
https://github.com/coturn/coturn/releases/tag/4.7.0
https://github.com/coturn/coturn/releases/tag/4.8.0
https://github.com/coturn/coturn/releases/tag/4.9.0
https://github.com/coturn/coturn/releases/tag/4.10.0

While here:

• Remove unnecessary PKGNAMEPREFIX.
• Merge INSTALL_PROGRAMs.
• Samplefy installation of the config.
• Merge MKDIRs.
• Remove unnecessary MKDIR.

PR: 294842
Approved by: blanket (fix 3 CVEs)
Security: CVE-2026-40613
Security: CVE-2026-27624
Security: CVE-2025-69217
Sponsored by: UNIS Labs
Co-authored-by: Vladimir Druzenko <vvd@FreeBSD.org>
MFH: 2026Q2