feat: add combo-box using slotted input

[web-padawan]

Description

This PR adds @vaadin/combo-box base class, Lumo and Material theme, and visual tests.

Fixes #2202

Breaking changes

• Removed deprecated render method

Note

Some logic is imported from vaadin-combo-box package:

• ComboBoxDataProviderMixin
• vaadin-combo-box-dropdown-wrapper
• Lumo and Material for combo-box dropdown

These will be updated in #2203, as well as JSDoc and missing TS typings.

Type of change

• Feature

[fhdhsni]

Some observations when testing the component:

1. number of available options is not announced when opening the listbox. I'm not sure how it can be fixed.
   Here is an example of a combo-box which announces the number of options. It uses adobe spectrum combo-box component.

2. It's a good idea to add aria-setsize and aria-posinset since the component supports lazy-loading.

3. when an option is selected, let's say foobar, it is announced as foobar unselected (VoiceOver chrome). On Safari it doesn't say unselected but it doesn't say foobar selected either, which would be more clear.

4. When going through the options, it doesn't announce which one is selected/not selected. You can test the previous example for a working case (Chrome announces not selected items, Safari announces the selected item)

5. The dropdown button should be accessible? it's not at the moment but doesn't seem a big deal. It can provide another way to open the list though. If we decided to make it accessible it should have aria-haspopup="listbox" attribute.

6. the input should have an aria-activedescendant attribute indicating which option is visually focused.

7. since home/end keys don't move the visual focus to the first/last option, up-arrow/down-arrow keys should wrap when the visual focus is on the first option or the last option.

8. aria-owns and aria-controls on the input referring to the listbox.

9. aria-haspopup="listbox" on the input, although apparently role=combobox adds that by default but I saw it being used in a lot of places in addition to the role=combobox (for example reach-ui). Maybe it's necessary for some screen readers.

10. listbox should have aria-labelledby/aria-label attributes

[web-padawan]

the input should have an aria-activedescendant attribute indicating which option is visually focused.

This and other related changes will be done as part of #2240

[vursen]

Removed deprecated render method

Removed processTemplates and corresponding tests

While the reason for removing the deprecated render method is pretty much clear, I don't truly understand why to also remove processTemplates().

Did we agree at any moment to stop supporting Polymer Templates even with the template renderer?

@tomivirkki @web-padawan

[tomivirkki]

Hmm...can't drop support for <template>s yet. The Flow counterparts also still depend on them (TemplateRenderer for example).

[web-padawan]

I will restore the <template> support and corresponding tests.

[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
37 Code Smells

No Coverage information
8.4% Duplication

[web-padawan]

Closing in favor of #2496