TreeTable: Make TreeTable accessible for ScreenReaders

Describe the bug

The TreeTable component is not accessible for screenreaders and behaves strangely. I tested it with the NVDA-Screenreader (https://www.nvaccess.org/download/) and tried to navigate it with the build-in shortcuts.

First thing to notice, is that the header of the table is a table for itself and the body of the table is a second table. If you add frozenColumns, you got 4 tables for one visible table. That makes it very confusing, if you use a screenreader.

It should be possible to navigate it as one table (CTRL + ALT + Arrow Left / Arrow Right / Arrow Top / Arrow Bottom to navigate between the cells).

If it is one table, the header will be read together with the corresponding cell. Example for a table that reads perfectly in Screenreaders: https://dequeuniversity.com/screenreaders/nvda-keyboard-shortcuts#nvda-speech_viewer

If you use the screenreader to navigate to the marked red cell, it will read something like "LeftBlock: row X Header column y content" --> "Reading: row 4 Task column 2 Stop Reading"

When the header is a table in itself, the screenreader cannot read the heading with the content, which makes it way harder to navigate.

Additionally, the key-bindings for left and right arrow to open or close the node interfers with the screenreaders ability to navigate the table.

Environment

All Environments

Reproducer

https://stackblitz.com/edit/fdghbm?file=package.json

Angular version

18.x

PrimeNG version

17.18.x

Build / Runtime

Angular CLI App

Language

TypeScript

Node version (for AoT issues node --version)

20.16.0

Browser(s)

No response

Steps to reproduce the behavior

Download and install NVDA (https://www.nvaccess.org/download/)
Open NVDA
Navigate to the TreeTable-Site (https://primeng.org/treetable#frozencolumns)
Press t to get to the next Table
See that frozenColumns-Header, frozenColumns, normal Header, normal table are all seperate tables
Try to navigate the table without looking at the screen.

Expected behavior

The table should behave like one big table, not like 2 or even 4 separate tables. The navigation with the screenreader should be seamlessly possible, like it is for example here: https://dequeuniversity.com/screenreaders/nvda-keyboard-shortcuts#nvda-speech_viewer

primefaces / primeng