Add functionality to default product section to accommodate more use cases

Problem

With Create a default section for showing products w... (#7293 - closed), we can now show any new product added to a subscription without having a specific product mapping on the frontend. We also cleaned up a few existing section to leverage the default product section in #9762 (closed).

However, there are a few more product sections which could use the default product section if we can handle some additional use cases:

1. Ability to define the columns that need to be shown in the default product section. Certain products like true-ups, professional services display different columns (i.e. purchase date instead of start date and end date).
2. Ability to show sub-text - used in true-ups, professional services.
3. Ability to show total quantity of product - used in GitLab product analytics, Enterprise agile planning.
4. Ability to show a different title than that defined as SKU name in Zuora - used for GitLab product analytics.

Proposal

We could add some sort of configuration on the backend for unmapped products. If a particular unmapped product needs special handling (one of the problems mentioned above), then we define the configuration for it against it's SKU id.

Result

We should be able to remove the Vue components on the frontend for products which do not have any actions like Buy more or Upgrade (or we don't expect them to have actions in the future) like Professional services, True-ups, Enterprise agile planning, GitLab product analytics etc.