Fixes microsoft/vscode-internalbacklog#1736

We still have to figure out where to best put these files

Reworking external opener implementation to allow configured openers to be called directly without a canOpen check

If the user has configured a specific external uri opener, we should always try to use that without first calling `canOpen` to filter down the list of openers.

This change also adds `ExternalUriOpenerEnablement` which allows an opener to mark itself as the preferred opener for a given uri. If only a single preferred opener is returned, it will be used automatically for that uri (although user configuration can override this)

Add test for case to assert that fetch should be scheduled again when a text buffer change occurs while the provider runs and the provider returns null

Do not show "Cannot reconnect. Please reload the window" if the cause is a handled RemoteAuthorityResolverError

This workbench service handles opening external uris. Unlike the core OpenerService, it also has logic for configuring a default opener and prompting if multiple openers are availble for a given uri

//cc @aeschli

Can't open, rename or delete files that contains ":" on linux (fix microsoft/vscode-remote-release#4227)

* Use RimRafMode.UNLINK in tests to avoid filesystem contention (#114024)

* Add `rimrafWithRetries` for tests which incorrectly continue writing to the fixture directory even after the test signals completion

* 💄 No need to pass in RimRafMode.UNLINK since that is the default

* Also retry in case of EPERM

* Add some logging to check if rimraf really fails 5 times

* Fix retry logic

* Improve BackupTracker disposing to avoid fs writes after the test finishes