While testing i noticed that when i add num: Long(12) in shell syntax and native to ejson and then back to shell, it changes it to num: NumberLong(12).

This is because the mongodb-query-parser package doesn't stringify it as `Long`:
https://github.com/mongodb-js/devtools-shared/blob/44c98f5395f4c60207619884a7700aed11c70dfe/packages/query-parser/src/stringify.ts#L93 
Let's update that. NumberLong was for legacy shell: https://www.mongodb.com/docs/mongodb-shell/reference/data-types/#long 

Let's make autocomplete work.