net-im/tox: Improve port
- Use upstream release archive
- Fix various dependency related issues
- Add USES= compiler:c++17-lang
- Utilize USES= cmake:testing
- Fix plist-issue, bash-completion
- Rework and modernize Makefile layout to closer follow Porters Handbook
PR: 284134
Approved by: portmgr (maintainer timeout, 2+ weeks)