Override machine metrics snapshot with sampler lock during build bundling

Fixed an intermittent crash where uploading a build could produce a build archive that the server could not process. The CLI was bundling machine_metrics.jsonl into the archive without holding the tuist.metrics-sampler file lock, so the copy could capture the file mid-write and end up with a bad CRC. Build uploads now snapshot the metrics file under the same shared lock used when reading samples, so the archive entry is consistent with the daemon and rejected uploads no longer happen for this reason.