yarn: Make `global` persist and fix global bin issue (#3206)
yarn: Make `global` persist and fix global bin issue (#3206)

- Yarn's global folder can be set via `yarn config set global-folder` (https://github.com/yarnpkg/yarn/pull/7056) and thus can be persisted. 
- ~~Since yarn's global bin creating procedure is still problematic (https://github.com/yarnpkg/yarn/issues/6902, **fixed by https://github.com/yarnpkg/yarn/pull/6954**),~~ The `.bin` folder in `global\node_modules` is a better path to add to env, and this can avoid the annoying problem when you install scoop in some place except `C:` (that the shims in global bin have wrong relative path pointer).
- If you install yarn via `scoop install yarn`, the `Yarn` folder in `$env:LOCALAPPDATA` is useless, and when you uninstall `yarn`, the `.yarnrc` is unused, so the manifest add `uninstaller.script` to remove them when you uninstall.
- For reconfiguration, please use `scoop update yarn -f` instead of `scoop reset yarn`.

- Close #2969
lukesampson/scoop,kodybrown/scoop,berwyn/scoop,nikolasd/scoop,rasa/scoop,coonce/scoop