feat(wayland): text input through zwp_text_input_v3

A window can now say that a text field has the focus and where its caret
is — Window::SetTextInput(active, caret rectangle in physical pixels,
purpose) — which is what opens the on-screen keyboard on a phone (Maliit
under KWin, squeekboard under phoc). What the input method produces comes
back as events: committed text as onTextInput, the composing text as
onPreedit (empty clears it), deletions around the cursor as
onTextInputDelete; done() applies them in the protocol's order. The state
a window wants is remembered and sent again whenever the keyboard focus
returns to it. The protocol's client code is generated with wayland-scanner
1.26.0 from wayland-protocols' text-input-unstable-v3.xml, under lib/ like
the others.

interfaces/Crafter.Graphics-Types.cppm

@@ -25,6 +25,15 @@ export namespace Crafter {
         Vector<float, 2> position;
     };
 
+    // The input method asks for bytes around the cursor to go (text-input-v3
+    // counts UTF-8 bytes).
+    struct TextDelete {
+        std::uint32_t beforeBytes;
+        std::uint32_t afterBytes;
+    };
+
+    enum class TextInputPurpose : std::uint8_t { Normal, Phone };
+
     struct ScaleData2D {
         Vector<std::int16_t, 2, 2> position;
         Vector<std::int16_t, 2, 2> size;