### Motivation
In some case, my k8s node only have 1 large capacity ssd, for deploying 1 bookie, I need:
- Partition the ssd into 2 disks, and make 2 pv over it.
- Just make 1 pv over it, but journal & ledgers under same mount path (this PR did)
Both can't isolate IO for journal & ledgers, so I prefer the second one for reusability.
### Modifications
values.yaml
- add `useSingleCommonVolume` option, default false
bookkeeper-statefulset.yaml
- mount the only PV to path `/pulsar/data/bookkeeper`
- use configured common storageClassName
bookkeeper-storageclass.yaml
- use configured provisioner for the common storageClass
### Others
This may not be an issue for everyone, if it's not necessary to merge, I'll just use it locally
### Verifying this change
- [x] Make sure that the change passes the CI checks.
It remains possible to override the current release namespace by setting
the `namespace` value though this may lead to having the helm metadata
and the pulsar components in different namespaces
Fixes#66
### Motivation
Trying to deploy the chart in a namespace using the usual helm pattern fails for example
```
kubectl create ns pulsartest
helm upgrade --install pulsar -n pulsartest apache/pulsar
Error: namespaces "pulsar" not found
```
fixing that while keeping the helm metadata and the deployed objects in the same namespace requires declaring the namespace twice
```
kubectl create ns pulsartest
helm upgrade --install pulsar -n pulsartest apache/pulsar --set namespace=pulsartest
Error: namespaces "pulsar" not found
```
This is needlessly confusing for newcomers who follow the helm documentation and is contrary to helm best practices.
### Modifications
I changed the chart to use the context namespace `.Release.Namespace` by default while preserving the ability to override that by explicitly providing a namespace on the commande line, with the this modification both examples behave as expected
### Verifying this change
- [x] Make sure that the change passes the CI checks.
