Dedicated key/command for word-based suggestions

[W4RH4WK]

In #21611 there's a lot of discussion about providing word-based suggestions along with IntelliSense. While this idea comes with unique challenges, I propose an alternative which might still be helpful to some people and also provides a (temporary) workaround for the mentioned issue.

Adding a dedicated key/command to bring up only word-based suggestions. This should work independent of the language that is used, as well as independent of any language servers that is enabled. The main reason for this is responsiveness. Especially with the C/C++ language server I sometimes have to wait multiple seconds for the suggestions to pop up, just to see that the wanted string is not listed. But word-based suggestions finds it instantly since that string is already in the same file.