Add .js suffix to all file imports

Summary:
Full context in ENG-2982, but basically Node 19 and Webpack 5 want you to explicitly specify the suffix.

To make this diff I ran a codemod script, which I'm not committing, but is documented in the task.

Test Plan: The way I ran the codemod script is documented in the task. I also tested this diff and the rest of the stack by running web, landing, keyserver, and native all together and making sure it still worked

Reviewers: atul, tomek

Reviewed By: atul

Differential Revision: https://phab.comm.dev/D6692