Create "migrate snippets" command that will automatically migrate all of a user's snippets

[pokey]

That can generate internal rep from above and use same output machinery. Will need to have a close look at schema of cursorless snippets vs community to understand what might be missing. @AndreasArvidsson may add support for scope-specific snippets (eg method v funk), but at the very least will not error out when the given field appears

As with #2354, if they have set custom snippet directory in community, use that dir instead of default