net/turnserver: Update 4.14.0 => 4.16.0

Port changes:

• Run turnserver as non-root by default.
• Pet port(lint|fmt|clippy).

PR: 297251, 296810
Reported by: Frank Wall <freebsd@moov.de>
Reported by Zixu Wu <zx@bv3.dev>
Approved by: Chris Hutchinson <portmaster@bsdforge.com> (maintainer)
Approved by: osa, vvd (Mentors, implicit)
Co-authored-by: Frank Wall <freebsd@moov.de>
Co-authored-by: Zixu Wu <zx@bv3.dev>
Security: GHSA-5538-7cxj-5jcc
MFH: 2026Q3

(cherry picked from commit 87d11fd7305cb245dff284e34be3a5c0c423aa60)