Building with Fastlane doesn't support notarization

Currently, the `build_and_upload_beta` lane doesn't support notarization and, since we want to distribute notarized betas to our testers, it can't be used.

We have to update it in order to handle notarization.

Start by locating the `build_and_upload_beta` Fastlane lane and reviewing how this macOS project currently handles beta distribution. The work is done when the lane supports notarization and can produce notarized betas for testers; the issue does not name a test or implementation file.

Written by the indexing model from the issue text.