Implement base-workspaces.

[mshima]

Overview of the feature request

It will be the base for generators that uses multiple applications like the workspace generator and deployments.
It should provide a few custom priorities:

  get [BaseWorkspaces.DEFAULT]() {} // for reference

  get [BaseWorkspaces.LOADING_WORKSPACES]({ workspaces }) {}

  get [BaseWorkspaces.PREPARING_WORKSPACES]({ workspaces, applications }) {
    workspaces.aConfig = applications.every(application => application.aConfig);
    workspaces.anotherConfig = application.some(application => application.anotherConfig);
  }

  get [BaseWorkspaces.WRITING]({ workspaces }) {}

Motivation for or Use Case

Simplify deployment generators.

Related issues or PR

#19978 (comment)

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[mshima]

@DanielFran bounty claimed https://opencollective.com/generator-jhipster/expenses/170967

[DanielFran]

@mshima approved