Is Zookeeper mandated for using Burrow?

Hi Team,

I am trying to use Burrow for my Kafka cluster but I didn't provide Zookeeper configuration since I might switch to KRaft mode soon and thought it was not mandatory to use Zookeeper.

My setup failed and my pod on K8s couldn't start and entered a CrashLoopBackOff issue and found the following in the pod logs:

```
Reading configuration from /etc/burrow
panic: No Zookeeper servers specified [recovered]
panic: No Zookeeper servers specified [recovered]
panic: No Zookeeper servers specified

goroutine 1 [running]:
main.handleExit()
/home/runner/work/Burrow/Burrow/main.go:63 +0xf8
panic({0xbeb8a0, 0xc000210a30})
/opt/hostedtoolcache/go/1.20.1/x64/src/runtime/panic.go:884 +0x213
go.uber.org/zap/zapcore.CheckWriteAction.OnWrite(0x0?, 0xc0001001a0?, {0x0?, 0x0?, 0xc00021a700?})
/home/runner/go/pkg/mod/go.uber.org/zap@v1.24.0/zapcore/entry.go:198 +0x65
go.uber.org/zap/zapcore.(*CheckedEntry).Write(0xc000200b60, {0x0, 0x0, 0x0})
/home/runner/go/pkg/mod/go.uber.org/zap@v1.24.0/zapcore/entry.go:264 +0x3ec
go.uber.org/zap.(*Logger).Panic(0x0?, {0xd26f47?, 0x0?}, {0x0, 0x0, 0x0})
/home/runner/go/pkg/mod/go.uber.org/zap@v1.24.0/logger.go:258 +0x59
github.com/linkedin/Burrow/core.configureCoordinators.func1()
/home/runner/work/Burrow/Burrow/core/burrow.go:96 +0x56
panic({0xbeb8a0, 0xebb050})
/opt/hostedtoolcache/go/1.20.1/x64/src/runtime/panic.go:884 +0x213
github.com/linkedin/Burrow/core/internal/zookeeper.(*Coordinator).Configure(0xc000232400)
/home/runner/work/Burrow/Burrow/core/internal/zookeeper/coordinator.go:64 +0x26b
github.com/linkedin/Burrow/core.configureCoordinators(0xc0002203c0, {{0xec26e0, 0xc000232400}, {0xec26b0, 0xc000206c60}, {0xec2500, 0xc00021a660}, {0xec25c0, 0xc000206cf0}, {0xec25f0, ...}, ...})
/home/runner/work/Burrow/Burrow/core/burrow.go:103 +0xb3
github.com/linkedin/Burrow/core.Start(0xc000220360?, 0xc00012bef0?)
/home/runner/work/Burrow/Burrow/core/burrow.go:151 +0x3dc
main.main()
/home/runner/work/Burrow/Burrow/main.go:114 +0x4d2
```

Does this mean I can't use Burrow without providing a Zookeeper config? What if I am using KRaft?

> **Burrow image used:** ghcr.io/linkedin/burrow/burrow:v1.6.0

> **Configurations**

```
[logging]
filename="logs/burrow.log"

[client-profile.myclient]
kafka-version="3.6.1"
client-id="borrow-client"
sasl="saslprofile"

[sasl.saslprofile]
username="myuser"
password="mypassword"
mechanism="SCRAM-SHA-512"

[httpserver.mylistener]
address=":8080"

[cluster.myclustername]
class-name="kafka"
servers=[ "my.single.server" ]
client-profile="myclient"
topic-refresh=60
offset-refresh=30
groups-reaper-refresh=30

[consumer.myconsumers]
class-name="kafka"
cluster="myclustername"
servers=[ "my.single.server" ]
client-profile="myclient"
offsets-topic="__consumer_offsets"
start-latest=true
group-allowlist=".*"
```

I will appreciate any help from the team or the community, TIA :")

Start with core/internal/zookeeper/coordinator.go and the coordinator setup in core/burrow.go, using the provided panic trace as the entry point. Determine whether Burrow's current configuration supports a Kafka cluster without ZooKeeper, including KRaft, and define the compatibility or implementation work needed before this can be considered done.

Written by the indexing model from the issue text.