Highlighting exit points only works on `return` in VSCode

[Veykril]

Companion issue to microsoft/vscode#127007 to keep track of the issue on our side.

Basically exit point highlighting is supposed to work when the cursor is either on a return, ? or -> token but VSCode currently doesn't send the document highlight request unless the cursor is on a return or at the end of an identifier followed by a ?.

cc #9375