dns/dnsdist: Update 2.0.2 => 2.0.3 (security)

While here:

• Drop backported patch since they're in new release
• Reduce portlint warnings by using increment for DISTFILES
• Use <bsd.port.options.mk> instead of <bsd.port.{pre,post}.mk>

Release notes:
https://blog.powerdns.com/2026/03/31/powerdns-dnsdist-1.9.12-and-2.0.3-released
Changelog:
https://www.dnsdist.org/changelog.html#change-2.0.3

PR: 294225
Reported by: Jordan Ostreff <jordan@ostreff.info>
Approved by: Ralf van der Enden <tremere@cainites.net> (maintainer)
Approved by: osa (mentor)
Security: CVE-2026-0396
Security: CVE-2026-0397
Security: CVE-2026-24028
Security: CVE-2026-24029
Security: CVE-2026-24030
Security: CVE-2026-27853
Security: CVE-2026-27854
MFH: 2026Q2