Feature: Allow to Persist table state (column order/width/visibility, sorting, filtering)

[DanielTrommel]

@w-ahmad Usability feature that I needed myself, and wanted to share, as probably more people may like to use this.

This PR adds

• a StateChanged event,
• a State get/set property to the TableView;
  • state includes all things the user can influence at runtime; column order, sorting,
• which interacts with a Helper to get/set the current column/sorting/filtering state in/from a State object
• that state object can be used to store to e.g. the AppSettings, using the JsonSerializer

Notes

• Designed to be opt-in, and minimal changes to existing code.
• the state setting code is forgiving; best effort processing (persisted state could (partially) mismatch after column changes by developer)
• matching is done for bound columns based on path (Tag is secondary, when multiple matches); for template columns the Tag/Name is used.

Column Visibility

Note that this State also includes "Visibility"; I don't think we have functionality yet to hide columns in a built-in fashion, do we?
I would love to add this as well, as with this PR it would allows users to modify a column, and persist their preferred order and visibility etc.

New Column

Furthermore, I would think these are great additionals to runtime configurability:

• We could allow (totally new!) columns to be added at runtime; based on the associated (abstract) type in the CollectionView, we could create a dialog where users choose a property to add a new column, and then obviously persist those across sessions. (This could be even more advanced, by using reflection to `walk' the model and choose a binding path)
• In addition, it would then also be good to allow columns to be renamed (the default property name might not do the functional context justice)

Grouping

Also the Grouping feature (this PR: #340) would be excellent to be end-user configurable (out-of-the-box), and persist-able. Of course the developer could set a default, but we could allow to change the grouping column via a context menu on the header of a column.
I hope you will consider to merge your implementation of the grouping 🙏, as it seems functionally very valuable have.

[DanielTrommel]

PS: to avoid merge conflicts with at least one other PR is saw, I added my new code somewhere sensible, but not at the end of existing files.

[DanielTrommel]

Just realized that TableView.FrozenColumnCount could also be a candidate to configure at runtime, and part of the state.
More properties like that?