FTL: Collect metadata about the stream

Fields normally used are:
```
type StreamMetadata struct {
AudioCodec string
IngestServer string
IngestViewers int
LostPackets int
NackPackets int
RecvPackets int
SourceBitrate int
SourcePing int
StreamTimeSeconds int
VendorName string
VendorVersion string
VideoCodec string
VideoHeight int
VideoWidth int
}
```

Start by locating the FTL stream-handling entry point and references to StreamMetadata. Determine how the listed audio, video, ingest, packet, bitrate, timing, and vendor fields can be collected. Done means the metadata is populated for an FTL stream and the relevant behavior is covered by existing or added tests; the issue names no files or tests.

Written by the indexing model from the issue text.