[Stateful:Indices:Index mapping page]Grouping issues for lists

[L1nBra]

Description
For users it should be clear when they are on the lists, how they are grouped, how many items are in them and on which item user is at the moment. Especially for the users using assisting technology, who cannot visually see elements on the page.

Preconditions
Stateful -> Indices -> Index mapping page is opened.
Use Screen Reader (NVDA).

Steps to reproduce

1.Navigate to Add field button by pressing Tab key.
2.Press Enter.
3.Navigate to Field type input in Pending fields section by pressing Tab key.
4.Press Enter.
5.Press down arrow key (many times).
6.Observe screen reader announcement.
7.Navigate to list with items below Pending fields section by pressing Tab key.
8.Press Tab (many times).
9.Observe screen reader announcement.

NVDA Speech Viewer + UI elements

Actual Result

• For Field type firstly screen reader announces "Pending fields 0 grouping"; when pressing down arrow key - on some elements it announces "1 of 9", on some "8 of 10", on some "9 of 11" (explanation: different total number of elements is announced even though it is one list); when user navigates to Dense vector item - it's announced "Geo-point Dense vector 8 of 10" (explanation: additional items are being announced, not only the one on which user is at the moment).
  For list below Pending fields section screen reader announces that it is list with 10 items, but then going through items - it is not announced on which item of 10 user is at the moment, only the item is announced.

Expected Result

• It should be clearly announced for the user what is in the group; for the lists it should clearly state on which element user is at the moment (f.e.: 1 of 10) and the total number of the items shouldn't be different on elements; only the item on which user is present is announced, no additional items.

Meta Issue

Kibana Version: 8.16.0-SNAPSHOT

OS: Windows 11 Pro

Browser: Chrome Version 129.0.6668.101 (Official Build) (64-bit)

Screen reader: NVDA

WCAG or Vendor Guidance (optional)

• Understanding SC 1.3.1: Info and Relationships (Level A)(https://www.w3.org/WAI/WCAG22/Understanding/info-and-relationships.html)
• Understanding SC 4.1.2: Name, Role, Value (Level A)(https://www.w3.org/WAI/WCAG22/Understanding/name-role-value.html)

Related to: https://github.com/elastic/search-team/issues/8256

[elasticmachine]

Pinging @elastic/kibana-accessibility (Project:Accessibility)