Add number formats for network throughput (Mbps/Gbps)

[bmuraykhi]

The number format dropdown offers MEMORY_TRANSFER_RATE_DECIMAL, which renders a bytes-per-second column in bytes (1024B => 1.024kB/s). There is no option that renders a rate in bits, even though network throughput is conventionally reported that way (Mbps/Gbps/Tbps).

Consequences today:

• A column already reporting bits/s has no matching format at all.
• A byte-rate column requires hand-writing × 8 in every metric expression to get Mbps.

Proposal: add two decimal (base-1000) throughput formats — one for columns holding bits/s, one for columns holding bytes/s that should display as bits.