[keyserver] Removing from the rust-node-addon gitignore and populate it

Summary:
This diff removes Cargo.lock file from the .gitignore in the rust-node-addon and populates this file. We should add a lock file to lock the dependencies versions and avoid possible errors due to the versions inconsistency.

Linear task: ENG-3048

Test Plan: Running yarn cleaninstall from the root of the project results in a successful build of the rust-node-addon library as a part of the dependencies.

Reviewers: ginsu, varun, jon, ashoat

Reviewed By: ashoat

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D6791