fix: TS program doesn't emit declaration files

[pavandv]

This PR addresses 2 main issues:

1. TS doesn't emit declaration files. TS isn't able to resolve the Source files passed to ts.createProgram, from federationOptions#exposes. The file paths mentioned in exposes may not always be relative to the cwd().
2. __types_index.json has wrong file paths that aren't in sync with the emitted .d.ts files.

Creating a Draft PR fixing #1. Will update the PR with #2 later today.