Allow snippets to control the scope to which they are applicable

[jrieken]

We know have solid information about the current position/cursor being in a string, in a comment, in a regex, and elsewhere. We should expose this to snippet authors such that their snippets can express where they want to show

[jrieken]

Strech for march...

[CoenraadS]

Could exposing this information about an arbitrary position being a string/comment etc also be available as an extension API?

[jrieken]

re #22661 (comment) that's actually a lot, lot more complex because token scan change a lot while you type and we would need to eagerly synchronize that to the extension host process which is quite expensive. There are ideas about tokenising in the ext host but nothing real yet