[AX][GTK] Implement Text interface for document-web

[GeorgesStavracas]

2a84947

[AX][GTK] Implement Text interface for document-web
https://bugs.webkit.org/show_bug.cgi?id=268154

Reviewed by NOBODY (OOPS!).

This patch changes slightly how the roles reported by the AT-SPI DOM
tree are available. The goal is to unify how browsers report roles on
their accessible trees. It makes WebKit mostly match what Firefox and
Chromium do.

It is based on three general rules discussed with Orca developers:

 1. Accessible objects that implements Text must also implement Hypertext
 2. Children of Hypertext implementors must implement Hyperlink
 3. The document-web object must implement Text

In practice, this makes all accessible objects under the document-web
object implement Hyperlink, and many more implement Text now.

* Source/WebCore/accessibility/atspi/AccessibilityObjectAtspi.cpp:
(WebCore::AccessibilityObjectAtspi::interfacesForObject):

2a84947

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	❌ 🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 gtk
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	❌ 🧪 gtk-wk2
	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2	❌ 🧪 api-gtk
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash 2a84947)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	❌ 🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 gtk
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	❌ 🧪 gtk-wk2
	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2	❌ 🧪 api-gtk
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim