* Use 'r+' with truncation when saving existing files on Windows

Opening a file with 'w' flag removes its alternate data streams. To
prevent this, extend the logic used for hidden files to all existing
files.

Fixes: https://github.com/Microsoft/vscode/issues/6363

* adopt truncate for saving as admin

This reverts commit 0e3a2219.

fixes #56550

do not attempt edit operation for read-only editors

Fixes #3948

Fixes #56735

fixes #56666

fixes #56806

fixes #53257

Fixes #55635

#56501

This reverts commit 315cce83.

fixes #48377

@import and url() link. Fix Microsoft/vscode#29899