chore(grid, pivot): add deprecation proxy for shouldGenerate to autoGenerate

[georgianastasov]

Related to #14315

This PR refactors the existing deprecation of the shouldGenerate property in the grid and pivot-grid components. It now acts as a proxy to the already existing autoGenerate property using getter and setter methods. This enhancement ensures backward compatibility and simplifies the transition process for users still relying on the deprecated property.

Additional information (check all that apply):

• Bug fix
• New functionality
• Documentation
• Demos
• CI/CD

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code (test guidelines)
• This PR includes API docs for newly added methods/properties (api docs guidelines)
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes (migrations guidelines)
• This PR includes behavioral changes and the feature specification has been updated with them