Add Option to Set Scratch PV Size

Currently, the scratch PV is hardcoded to be 1Gi.

@subughimire420 currently has an instance of BlueAPI  (P51) which is consuming 98% of this.

In order to mitigate storage issues, an option to manually set the size of the scratch PV must be exposed.

## Acceptance Criteria
- When deploying through Helm, the size of the scratch PV can be set to an arbitrary value.
