rpk: introduce rpk redpanda start --mode container

[r-vasquez]

Cover letter

Introducing --mode container for rpk redpanda start

For full context, see PRD: https://docs.google.com/document/d/1qC6K0xvC3i3JgI-LMAWCyWlxQZ8KvM8ABthujWFDQ74

Usage

# Container Mode:
$ rpk redpanda start --mode container

# Mode Validation:
$ rpk redpanda start --mode foo
Error: unrecognized mode "foo", use --mode help for more info"

Documentation

$ rpk redpanda start --mode help
Mode uses well-known configuration properties for development or tests 
environments:

--mode container
    Bundled flags:
        * --overprovisioned
        * --reserve-memory 0M
        * --check=false
        * --unsafe-bypass-fsync
    Bundled cluster properties: 
        * auto_create_topics_enabled: true
        * group_topic_partitions: 3
        * storage_min_free_bytes: 10485760 (10MiB)
        * topic_partitions_per_shard: 1000

After redpanda starts you can modify the cluster properties using:
    rpk config set <key> <value>

Backport Required

• v22.2.x

UX changes

• overprovisioned is now enabled by default when Redpanda.DeveloperMode is enabled (redpanda.developer_mode : true in redpanda.yaml)

#5997 contains the latest release notes.

Release notes

• none

[r-vasquez]

Failure is #5968

[r-vasquez]

/backport v22.2.x

[BenPope]

If there are no release notes, can you include the * none bit, please.

[r-vasquez]

@BenPope I just added the release note, we iterated a bit with the naming/functionality of this feature and I forgot to add it at the end.