Support configuring tolerations in helm chart

[kate-osborn]

Is your enhancement request related to a problem? Please describe.
There's no way to define tolerations for the NGF Pod in the helm chart.

What would you like to be added:
Add tolerations in the helm chart values.

Why this is needed:
Allows users to configure tolerations for the NGF Pod. Tolerations allow the scheduler to schedule pods with matching taints. This is needed for systems that use taints for scheduling.

One use case is described in PR #1192, where there is a separate node pool for system services that has taints applied. In order for NGF to be scheduled on this node pool, tolerations need to be applied to the Pod.