libservo: Extend SiteDataManager::clear_site_data to clear localStorage (full)

{"fail_fast": false, "matrix": [{"name": "Linux (Unit Tests, Build libservo, WPT, Bencher)", "workflow": "linux", "wpt": true, "profile": "release", "unit_tests": true, "build_libservo": true, "bencher": true, "coverage": false, "build_args": "", "wpt_args": "", "number_of_wpt_chunks": 20}, {"name": "Windows (Unit Tests, Build libservo)", "workflow": "windows", "wpt": false, "profile": "release", "unit_tests": true, "build_libservo": true, "bencher": false, "coverage": false, "build_args": "", "wpt_args": "", "number_of_wpt_chunks": 20}, {"name": "Android", "workflow": "android", "wpt": false, "profile": "release", "unit_tests": false, "build_libservo": false, "bencher": false, "coverage": false, "build_args": "", "wpt_args": "", "number_of_wpt_chunks": 20}, {"name": "OpenHarmony", "workflow": "ohos", "wpt": false, "profile": "release", "unit_tests": false, "build_libservo": false, "bencher": false, "coverage": false, "build_args": "", "wpt_args": "", "number_of_wpt_chunks": 20}, {"name": "Lint", "workflow": "lint", "wpt": false, "profile": "release", "unit_tests": false, "build_libservo": false, "bencher": false, "coverage": false, "build_args": "", "wpt_args": "", "number_of_wpt_chunks": 20}]}

Author: janvarga