Refactor Taranta frontend to improve performance of running dashboards

Value is expected to come from:

• reduction of technical debt based on:
  • the new architecture taking advantage of React native ways to handle propagation of changes;
  • a better test coverage of the store (with actions, accessors and modifiers of the new store being better tested)
  • better documentation;
• an enhanced Dashboard sub-app that could support users interacting with devices that have many attributes that change very frequently. 

Given the expected effort to complete this refactoring (see my comment below) these benefits will be achieved in full only when the refactoring will complete. At the end of PI18 the benefits will be limited because of the small number of widgets that will be refactored.

The refactor of Taranta will be limited to the Dashboard sub-app (now the Devices has already been refactored along these lines):

• the new store of Dashboards will be restructured as was done for Devices and will contain data frames produced by TangoGQL;
• the rendering of dashboards will be based on the new mechanism based on new React guidelines for useReducer and useDispatch functionalities;
• code will be reused as much as possible between Devices and Dashboards.
• widgets will be refactored to take advantage of these changes.

From an external p.o.v. the functional aspects of the behaviour of Taranta will be exactly the same as before. Also the same dashboards can be reused as is.

Widgets affected by the refactoring in PI18 will be

• Label
• Box
• Attribute Display
• Timeline
• Tabular
• Command Array
• Command File
• Spectrum Table
• Attribute Writer Dropdown

Variable and Variable selector as a stretch. 

This means that dashboards based only on such widgets can be used and users will enjoy the performance boost entailed by this refactoring.

Widgets successfully refactored:

• Label
• Box
• Attribute Display
• Timeline
• Tabular
• Command
• Command File
• Spectrum Table
• Attribute Writer Dropdown

Performance improvement:

Tests and docs:
https://gitlab.com/ska-telescope/ska-tango-taranta-group/ska-tango-taranta-dashboard-pipeline/-/jobs/4093689198

https://taranta.readthedocs.io/en/latest/