Add nav to the selectable elements for the group block

[carolinan]

What problem does this address?

I am splitting this out of #57664

There seems to be a consensus that the nav HTML element should be added to the list of selectable elements in the Advanced section of the settings for the group block. Currently, the tag can only be added with code.
The purpose of the change would be to make it easier for advanced users who are not developers to create accessible navigations.

Even if there is consensus among contributors, there is still one important aspect that must to be solved:
When multiple nav elements exists on a page, the user needs to be able to distinguish the different nav elements, or, in other words,
users needs to know the purpose of the navigation.
The main navigation, the next and previous posts in a query, the comment pagination etc. and any custom navigations that the users adds, they need to be identifiable.

In the linked PR for the post navigation block, this is solved by adding a block attribute and an option where the user can customize the aria-label for the nav element:

<InspectorControls group="advanced">
				<TextControl
					__next40pxDefaultSize
					__nextHasNoMarginBottom
					label={ __( 'Navigation name' ) }
					value={ ariaLabel || __( 'Posts' ) }
					onChange={ ( newLabel ) =>
						setAttributes( { ariaLabel: newLabel } )
					}
				/>
			</InspectorControls>

How should this be solved for the group block?

---

WCAG: Using ARIA landmarks to identify regions of a page
WordPress.org Theme requirement: ARIA Landmark Roles

[carolinan]

@fabiankaegy @t-hamano @draganescu @talldan

[t-hamano]

The Group block has ariaLabel block support, but this block support doesn't provide a UI. What if we add the control for ariaLabel only if tagName is nav?

I created a branch to test this: https://github.com/WordPress/gutenberg/compare/group-aria-label?expand=1

3b3f3b33891bec1c95d54304227b2afe.mp4

[carolinan]

@t-hamano I would support such a change to the group block.

[bacoords]

+1 In support of this. There should be the ability to put lists and other blocks inside a nav element without relying on the core navigation block or a custom block