Fixes #10292

From VDateField and VWindow

Based on vaadin/flow#2834

Make focus circulate in modal dialog to improve accessibility

* HasItems.setItems(T... items) should allow edits

Arrays.asList() creates a immutable Arrays.ArrayList, preventing users from doing dataProvider.getItems() and updating the returned collection. This makes it impossible to keep the same data provider, update it and keep the filters & sorting, and then just call dataProvider.refreshAll() to get changes visible. We should not require users to create a new data provider in this case.
This is the same for DataProvider.ofItems(T... items)

* fix missing whitespace from test error message

* Relax TreeGrid and Tree members access modifiers.

Fixes #10292

* Fixes after review

Because VConsole is deprecated and it recommends using Logger instead

In some places, getWidget() is called many times, and I believe this can
have a litte performance improvement, since in some cases
super.getWidget() is called more than once.

Fixes #10214

* add Grid#Column#get/setAssistiveCaption

* fix test and update doc

* move testGridAssistiveCaption to GridTest

* delete test file

* delete test file

* Delete GridAssistiveCaptionTest.java

* Create GridAssistiveCaptionTest

* Create GridAssistiveCaption

* Rename GridAssistiveCaption to GridAssistiveCaption.java

* Rename GridAssistiveCaptionTest to GridAssistiveCaptionTest.java

* Reformat using eclipse

Also improve naming by replacing one-letter variable names.

Also use "event" as the name for events

* Variable names to conform to naming convention.

* Use static constants where it makes sense

* Add contribution guideline

* Make suggested improvements to CONTRIBUTING.md

* Add link to good first issues and project setup

* Small update to CONTRIBUTING.md

* adds simple fix for missing label text in grid select checkboxes

* updated comment and wording

* Fix bad grammar in declarative documentation

* Fix typos

* Unlock panel caption div hacking

Fixes #10119

* Javadoc formatting fix

* Grid column to be sortable when implemented/supported
* Fix GridDeclarativeTest
* Parameterize to Grid<Person>
* Revert Parameterize to Grid<Person>, JDK with generics.
* Assertions for other columns
* Fix test

Fixes #8792

* Grid.removeColumn() not to fail silently (Fixes #8056)

* Compilation with JDK

* Fix removeColumnByColumn_alreadyRemoved test

* Use ExpectedException

Remove "java" from code example

* AbstractDateField.formatDate to be abstract

Remove invalidDateString paramter, as it can be deduced

* Fix test

* Remove AbstractDateField.getResolutionVariable

VAbstractTextualDate: rename updateDateVariables() to updateBufferedResolutions()

* Revert to use fixed value of MONDAY.

* release notes

* updateAndSendBufferedValues()

* Missed call to updateAndSendBufferedValues();

* release note

* Added the possiblity of defining a Field as Required without
setting an error message.

* Added @since to asRequired()

* Add droped paragraphs and see tag for asRequired(String)

* Fix typos

* Fix

* Check whether className is of type string

* Move string type checker method to widget util

* Fix formatting of WidgetUtil

* Break svg into lines

* add role="row" and role="gridcell"

* optimize code and add additional rows for the header

* add simple test

* improve code and add rowgroup

* add debug log

* add more log to test

* remove debug test info and add role before appending to tr

* wording - change contains to contain

* create enum for magic strings, change comments and method signature

* rename enum to be singular and rename param roleName to role

* update javadoc, rename and make enum public

* Use .toLowerCase and .toUpperCase(Locale.ROOT)

* Spaces

* add spaces after if(

* Fix HTML tags inside code in javadoc

* only modify <table> and <tr>

* Fix javadoc

* Scheduler.ScheduledCommand and RepeatingCommand to be lambda

* Restore <table> in javadoc

* Fix docs

* Add spaces after 'if' and 'for' in JavaScript

* Revert to old format

* Remove whitespaces

* Simplify lambda expressions

And remove unneeded 'return' keyword.

* Format

Fixes #9763
Fixes #9978

Fixes #9200

Fixes #9792