[RW2] receive: Metadata should not be appended to WAL unless feature flag is used. #17468
Description
Metadata WAL records (https://prometheus.io/docs/prometheus/latest/feature_flags/#metadata-wal-records) is still optional and in fact, problematic (#15911)
See:
prometheus/storage/remote/write_handler.go
Line 451 in 784ec0a
Noticed during our mentoring call with @pipiland2612 and @saswatamcode
Additionally, this metadata path with scrape loop is omitted, which is probably separate issue -- depending what we do with #17191