Split out from #77131
The current webview editor api is very procedural. This model has some problems when it comes to supporting editing resources, but actually does make a lot of sense for webviews that aren't backed by real file system resources. For example, if you have a webview that edits some document in the cloud, you should not be required to implement a custom file system provider just to enable basic saving.
This change moves the `onWillSave` and `webviewEditorState` properties back onto `WebviewPanel` instead of keeping them specific to `WebviewEditor`. The save implementation does not fully work yet, as the will require #81521
This fixes an issue where webviews for custom editors did not have any associated extension information, which caused them try reading `file:` uri resources instead of remote uri resources
* Custom Editor exploration
For #77131
Adds a prototype of custom editors contributed by extensions. This change does the following:
- Introduces a new contribution point for the declarative parts of a custom editor
- Adds API for registering a webview editor provider. This lets VS Code decided when to create a webview editor
- Adds an `openWith` command that lets you select which editor to use to open a resource from the file explorer
- Adds a setting that lets you say that you always want to use a custom editor for a given file extension
- Hooks up auto opening of a custom editor when opening a file from quick open or explorer
- Adds a new extension that contributes a custom image preview for png and jpg files
Still needs a lot of UX work and testing. We are also going to explore a more generic "open handler" based approach for supporting custom editors
Revert
* Re-use existing custom editor if one is already open
* Don't re-create custom editor webview when clicking on already visible custom editor
* Move customEditorInput to own file
* First draft of serializing custom editor inputs
* Use glob patterns instead of simple file extensions for matching custom resoruces for custom editors
* Add descriptions
* Try opening standard editor while prompting for custom editor
* Make sure we hide image status on dispose
* Make sure we restore editor group too
* Use glob patterns for workbench.editor.custom
* Allow users to configure custom editors for additional file types
* Use filename glob instead of glob on full resource path
* Adding placeholder for prompt open with
* Add enableByDefault setting for editor contributions
* Enable custom editors by default and add `discretion` enum
Changes `enableByDefault` boolean to a `discretion` enum. This should give more flexibility if we want other options (such as forcing a given custom editor to always be used even if there are other default ones)
* Allow custom editors to specify both a scheme and filenamePattern they are active for
* Rework custom editor setting
* Don't allow custom editors to be enabled for all resources by a config mistake
* Replace built-in image editor with one from extension
* Adding reopen with command
* Improve comment
* Remove commented code
* Localize package.json and remove image
* Remove extra lib setting from tsconfig
Fixes#79492
Simplifies view state management logic in `mainThreadWebviews` to:
* Not be stateful
* Handle cases where a webview's view state changes through a more complex means (see #79492 for an example of this)
