feat(language-service): auto insert feature does not abstract selection

[johnsoncodehk]

In the previous auto insertion implementation, @volar/vscode always issued requests with the end position of the changed range as a parameter. Based on whether the current selections include the end position of the changed range, it determines whether to insert the text into the selections or the end position of the changed range.

Now it is changed to always issue requests with the selection position and always insert the text into the selections. LanguageServicePlugin are responsible for determining whether the selection is at the end position of the changed range to determine whether to provide auto insert text.

This will resolve the limitation of not being able to achieve vuejs/language-tools#4140 downstream.