[bean completion proposals] improve performance of additional edits showing up

[martinlippert]

There is a significant lag between the completion being activated and the additional edits showing up in the editor. This causes a slightly weird and irritating moment, since additional text edits happen in the editor at a moment that is somewhat disconnected from the user interaction (of selecting the proposal). This lag also causes difficulties in a fast and fluent editing experience, for example when adding a method invocation to the bean variable that got introduced by the completion.

[BoykoAlex]

Hmm... I don't know how much we can do here. There might be an option to show the main edit with the additional edit to appear simultaneously at the time when the additional edit usually shows up, i.e 300-400ms after the proposal is invoked.