List/Tree: Add option to use role=form, explore others (support input elements, single 'level')

[cleidigh]

The tree and list widgets use aria role=tree which has two issues:

• Several tree users quick open, select box and now the new settings editor
  are not multilevel trees, screen readers always present them as such levels branches et cetera
• ARIA tree does not seem to explicitly support editable elements within the tree.
  Some specification references site a tree has read-only.

It it appears readers attempt to do their best, but for example these input elements
are not interpreted in the accessibility tree correctly with Electron 2.x and NVDA and voiceover
While Electron 3 beta with updated chromium does do better (see @joaomoreno comments on buttons) , also according to my experiments it is still not clear it is valid ARIA structure to have editable elements in a tree.

Debug Output:
NVDA initialized
INFO - globalCommands.GlobalCommands.script_navigatorObject_devInfo (15:36:12.450):
Developer info for navigator object:
name: u'Files Auto Save Delay, Setting'
role: ROLE_TREEVIEWITEM
states: STATE_SELECTABLE, STATE_FOCUSED
IAccessible accRole: ROLE_SYSTEM_OUTLINEITEM
IAccessible accState: STATE_SYSTEM_SELECTABLE, STATE_SYSTEM_FOCUSED, STATE_SYSTEM_VALID (2097156)

Input under form: (normal system editable state)

NVDA initialized
INFO - globalCommands.GlobalCommands.script_navigatorObject_devInfo (15:32:36.880):
Developer info for navigator object:
name: u'Files Auto Save Delay, Setting'
role: ROLE_EDITABLETEXT
states: STATE_FOCUSABLE, STATE_EDITABLE, STATE_FOCUSED
IAccessible2 role: ROLE_SYSTEM_TEXT
IAccessible2 states: IA2_STATE_SELECTABLE_TEXT, IA2_STATE_OPAQUE, IA2_STATE_EDITABLE, IA2_STATE_SINGLE_LINE (13320)

For the settings editor to work correctly with the screen reader I had to users
role=form and set the individual elements roles in certain cases. Experimentally
I also suppressed the aria attributes for trees level, position et cetera.

Proposal:

• add option to tree to use role = form
• remove tree oriented attributes when the form is used

Subsequently I think we should explore options for treegrid, grid and listbox

Related:
#57274 - lists with one levels
#53923 - aria-selected for list
#52682 - labeling on buttons in tree
#54836 - labeling within tree
#52390 - button roles within tree

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