Allow setting the update strategy for the API server in the HELM chart

Currently, the Dependency-Track Helm chart always uses the default strategy "RollingRelease" to update the StatefulSet or Deployment of the API server. We would like to be able to set this strategy ourselves.

**Current behavior**
No value is set, so kubernetes defaults are applied, depending on the deploymentType set in the values.yaml:
https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/#update-strategies
```
updateStrategy:
rollingUpdate:
partition: 0
type: RollingUpdate
```
https://kubernetes.io/docs/concepts/workloads/controllers/deployment/#strategy
```
strategy:
rollingUpdate:
maxSurge: 25%
maxUnavailable: 25%
type: RollingUpdate
```

**Desired behavior**
We would like to add a parameter to the values.yaml that allows setting this to a different value. For example when using a Deployment:
```
strategy:
type: Recreate
```

If this feature is of interest, we can create a PR with the needed changes.