Fix test jobs skipping when only one platform is selected in PRs (#55915)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55915

Addresses a design gap with conditional Android/iOS test runs ([#55449](https://github.com/facebook/react-native/pull/55449)). `build_npm_package` depended on both Android and iOS prebuilds, causing platform-specific E2E tests to be skipped unnecessarily.

Fixed by allowing `build_npm_package` to optionally skip bundling Apple prebuits, and updating the dependencies of the E2E test jobs.

Changelog: [Internal]

Reviewed By: cortinico

Differential Revision: D95218910

fbshipit-source-id: 29dd91b773a567ccf83c1888250493773232140d