cluster features describe: one row per feature, with what the level means - #79

cluster features describe printed SUPPORTED rows and then FINALIZED rows, four columns each, with the finalized level repeated as MIN and MAX. It is now one row per feature, the five numbers the Kafka script prints plus what the finalized level means, from kversion's new feature table (franz-go #1462):

FEATURE                           SUPPORTED-MIN  SUPPORTED-MAX  FINALIZED  EPOCH  DESCRIPTION
group.version                     0              1              1          1      the consumer rebalance protocol (KIP-848)
metadata.version                  7              27             27         1      4.1-IV1: replica fetcher sends Fetch v18 (KIP-1166)
share.version                     0              1              0          1      share groups off
transaction.version               0              2              2          1      epoch bump per transaction (KIP-890)

A feature the cluster has not enabled is at FINALIZED 0. A broker that has not learned the cluster's levels (epoch -1) prints FINALIZED, EPOCH, and DESCRIPTION as unknown. DESCRIPTION is free text in awk, like misc errcode's.

franz-go and kfake move to master, which also brings kfake's client metrics subscriptions: client-metrics alter|describe|list|delete now work against kcl fake, and their tests and the walkthrough exercise them instead of pinning INVALID_REQUEST.

Changelog

CHANGED

• cluster features describe prints one row per feature: SUPPORTED-MIN, SUPPORTED-MAX, FINALIZED, EPOCH, DESCRIPTION; it printed SUPPORTED then FINALIZED rows of KIND NAME MIN-VERSION MAX-VERSION. JSON keys: feature, supported_min, supported_max, finalized, epoch, description.
• kcl fake stores client metrics subscriptions, so client-metrics alter|describe|list|delete work against it.

UPSTREAM

• franz-go and kfake at master: kversion feature levels per release, kfake client metrics subscriptions, kfake ApiVersions advertising the features of its --as-version.