Don't run setDirty while IME input is unconfirmed.

[guttyon]

Fixes #164351
The following process has been added to solve this issue.

• Added unconfirmed flag, unconfirmed=true on onCompositionUpdate event and unconfirmed=false on onCompositionEnd event.
  https://github.com/guttyon/vscode/blob/f0323c2e67fc6506f0b67cd821ea4f6036063a56/src/vs/editor/browser/controller/textAreaInput.ts#L312
  https://github.com/guttyon/vscode/blob/f0323c2e67fc6506f0b67cd821ea4f6036063a56/src/vs/editor/browser/controller/textAreaInput.ts#L343
• When unconfirmed=true, setDirty(true) is not executed.
  https://github.com/guttyon/vscode/blob/f0323c2e67fc6506f0b67cd821ea4f6036063a56/src/vs/workbench/services/textfile/common/textFileEditorModel.ts#L606
• Replace command is now generated even when unconfirmed=false.
  https://github.com/guttyon/vscode/blob/f0323c2e67fc6506f0b67cd821ea4f6036063a56/src/vs/editor/common/cursor/cursorTypeOperations.ts#L285

[guttyon]

Fixes #164351 (comment)
The following process has been added to solve this issue.

• Canceling IME input results in changes === []. The result of the append function is whether that is the case or not.
  https://github.com/guttyon/vscode/blob/0c358f59fc4f4c615f155bba4f4c8729ae86b215/src/vs/editor/common/model/editStack.ts#L195
• Added a function to remove the last element from the _past stack.
  https://github.com/guttyon/vscode/blob/0c358f59fc4f4c615f155bba4f4c8729ae86b215/src/vs/platform/undoRedo/common/undoRedoService.ts#L572
  https://github.com/guttyon/vscode/blob/0c358f59fc4f4c615f155bba4f4c8729ae86b215/src/vs/platform/undoRedo/common/undoRedoService.ts#L364
• Added code to take the result of the append function and remove the last element from the _past stack if changes === [].
  https://github.com/guttyon/vscode/blob/0c358f59fc4f4c615f155bba4f4c8729ae86b215/src/vs/editor/common/model/editStack.ts#L440

This commit can be applied independently of the first commit.

[alexdima]

This is a huge change that brings the knowledge of IME (via the unconfirmed flag) to the world. I am not convinced of doing something very special for IME here. Also the file is dirty when not using IME and pressing for example A and then pressing Backspace. In other words, the dirty flag is not text buffer content based.

The proposed change is huge and I think a much more elegant solution would be to do something around equality. Perhaps we can compute the text model's sha1 in the web worker or something like that.

[guttyon]

Thank you for your review.

There were too many changes to propagate the unconfirmed flag. I will PR again when I come up with a solution with fewer changes.

What about my second comment: #164366 (comment)

I think this commit has relatively few changes.

[alexdima]

What about my second comment: #164366 (comment)

I think the right way to go here is to change the isDirty implementation in the workbench to be content based. Perhaps the TextFileEditorModel could remember the sha1 of the contents of the file on disk. Then, it can optimistically set isDirty using the current rules it already has, but it could kick off a sha1 computation on a web worker. If the computed sha1 is equal to the file on disk sha1, ti could mark the file as not dirty.