7102: Fix completion of Default struct update syntax r=Veykril a=nick96
Previously the inserted text was always `..Default::default()` which ends up as `...Default::default()`
if `.` was typed. Now checks if the current token is `.` and inserts `.Default::default()`
if it is, so `..Default::default()` is correctly completed.
I think there's probably a better way to implement this context aware completion because I've seen it in other parts of rust-analyzer as a user but I'm not sure how to do it.
Fixes#6969
Co-authored-by: Nick Spain <nicholas.spain@stileeducation.com>
f687d738be