security/libssh2: Update to 1.11.1

• Update MASTER_SITES, use GitHub as primary and upstream main website as fallback
• Fixes CVE-2023-48795
• Convert to CMake for faster builds and cleaner port Makefile
• Make static library option (non default)
• Enable OpenSSL support by default (optional)

PR: 282147
Approved by: portmgr (maintainer timeout, 2+ weeks)