chore(cli): @fern-api/openapi-ir-to-fern is browser compatible

[amckinney]

This is branched off #5299

This updates the @fern-api/openapi-ir-to-fern package to be browser compatible. This involves a few changes:

1. Update @fern-api/importer-commons to be browser compatible.
2. Remove the dependency on @fern-api/openapi-ir-parser.
   • Common utilities between openapi-ir-to-fern and openapi-ir-parser are now placed in the @fern-api/openapi-ir package.
3. Add the relative function to @fern-api/path-utils.