egui_extras::Table improvements (#2369)

* Use simple `ui.interact` for the resize line

* Introduce TableReizeState

* Simplify some code

* Add striped options to table demo

* Auto-size table columns by double-clicking the resize line

* Table: add option to auto-size the columns

* Table: don't let column width gets too small, unless clipping is on

* egui_extras: always use serde

Otherwise using `get_persisted` etc is impossible,
and working around that tedious.

* Avoid clipping last column in a resizable table

* Some better naming

* Table: Use new `Column` for setting column sizes and properties

Also make `clip` a per-column property

* All Table:s store state for auto-sizing purposes

* Customize each column wether or not it is resizable

* fix some auto-sizing bugs

* Fix shrinkage of adaptive column content

* Rename `scroll` to `vscroll` for clarity

* Add Table::scroll_to_row

* scroll_to_row takes alignment

* Fix bug in table sizing

* Strip: turn clipping OFF by default, because it is dangerous and sucks

* Add TableBody::mac_rect helper

* Table: add options to control the scroll area height.

* Docstring fixes

* Cleanup

crates/egui_extras/src/datepicker/button.rs

@@ -2,8 +2,7 @@ use super::popup::DatePickerPopup;
 use chrono::{Date, Utc};
 use egui::{Area, Button, Frame, InnerResponse, Key, Order, RichText, Ui, Widget};
 
-#[derive(Default, Clone)]
-#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[derive(Default, Clone, serde::Deserialize, serde::Serialize)]
 pub(crate) struct DatePickerButtonState {
     pub picker_visible: bool,
 }