File does not reload in editor when quickly changed externally after making modifications (fixes #12077)

**Bug**
Some regression since 1.9 caused the scroll preserve behavior of webviews to stop working in certain cases. There appears to be a race condition where `newFrame.contentDocument.body` does not exist when the scroll update code is called

**Fix**
Instead of using a timeout, update the scroll position when `DOMContentLoaded` is fired from the webview window

Fixes #21491

-  id is pub.name. name in lower case.
- use id to match sync installed extension with gallery extension
- use id to identify extension while installing and uninstalling
- Clean up
- Remove IExtensionIdentity
- Add util methods to create gallery id and local extension id

fixes #21149

fixes #21369

fixes #21082
fixes #21329

fixes #21379

Closes Microsoft/vscode-go#814
Signed-off-by: NOleg Bulatov <oleg@bulatov.me>