Allowing configuring a global `nodeselector`

**Is your feature request related to a problem? Please describe.**
We currently run a multi-arch (we want to migrate to arm64, but few of the services are not compatible yet) setup. Pulsar does not seem to be compatible with arm64 arch and requires scheduling them on amd64 machines. To do so, we need to explicitly this a configuration in each component. Configure a single global configuration would help!

**Describe the solution you'd like**
A global `nodeSelector` configuration which is applied to each enabled component if a `nodeSelector` is not configured for them (i.e. nodeSelector on component takes precedence).

**Describe alternatives you've considered**
Setting `nodeSelector` for each component individually.

**Additional context**
This seems to be a standard for a service with multiple components?

The issue does not name specific files; start by searching the chart values and templates for each component's nodeSelector setting. Add a shared global selector with component-specific values taking precedence, then verify rendered manifests for enabled components use the expected scheduling selector.

Written by the indexing model from the issue text.