converters/simdutf: Update to 5.3.7

• Add USES= pathfix to fix install path of .pc files
• Add USES= python:build,test as python is executed during build and test build
• Remove BENCHMARKS as it depends on external library/header from base64 (https://github.com/aklomp/base64 ) that isn't ported
• Define USES= compiler:c++17-lang
• Integrate TEST option into ports framework
• Some minor layout changes for better readability

Changelog: https://github.com/simdutf/simdutf/compare/v5.2.8...v5.3.7

PR: 280821
Reviewed by: fuz (maintainer)