Fix non-letter key input in tcore mode

The TIZEN_CORE_WL_EVENT_KEY_DOWN/UP listeners in
TizenWindowTcoreWl::RegisterEventHandlers were passing the wrong
strings into view_delegate_->OnKey(), so punctuation keys
(period, minus, equal, etc.) silently dropped when the IME panel
was hidden.

OnKey's signature is (key, string, compose, ...) where 'string'
is expected to be the printable character produced by the key.
TextInputChannel::HandleKey relies on
`strlen(string) == 1 && IsAsciiPrintableKey(string[0])` to
forward the character to the active TextInputModel.

The ecore_wl2 handler maps:
  key    <- key_event->key       (XKB symbol, e.g. "period")
  string <- key_event->string    (composed char, e.g. ".")
  compose <- key_event->compose

The tcore handler was passing:
  key    <- keyname              (key name, often == keysymbol)
  string <- keysymbol            (XKB symbol "period", strlen != 1)
  compose <- compose

For alphanumeric keys keysymbol is a single character ("a",
"1"), so the fallback in HandleKey() happened to fire. For
punctuation keys keysymbol is the symbol name ("period",
"minus", "equal"), strlen > 1, and the printable-fallback
branch is skipped, so nothing ever reaches the engine.

Pass keysymbol as 'key' and compose (the composed UTF-8 result)
as 'string', matching the ecore_wl2 contract. The IME path keeps
working independently because tizen_core_imf_context_filter_event
does its own keysym -> UTF-8 translation internally.

Author: JSUYA

flutter/shell/platform/tizen/tizen_window_tcore_wl.cc

@@ -674,7 +674,15 @@ void TizenWindowTcoreWl::RegisterEventHandlers() {
               self->input_method_context_->HandleTcoreWlEventKey(event, true);
         }
         if (!handled) {
-          self->view_delegate_->OnKey(keyname, keysymbol, compose, modifiers,
+          // Match TizenWindowEcoreWl2 OnKey arg semantics:
+          //   param 1 (key)    = XKB key symbol name (e.g. "period")
+          //   param 2 (string) = composed printable string (e.g. ".")
+          // tcore's keysymbol corresponds to ecore's key_event->key, and
+          // tcore's compose corresponds to ecore's key_event->string.
+          // Passing keysymbol as `string` breaks the printable-key fallback
+          // in TextInputChannel::HandleKey() for keys whose symbol name is
+          // multi-char ("period", "minus", "equal", ...).
+          self->view_delegate_->OnKey(keysymbol, compose, compose, modifiers,
                                       keycode, dev_identifier, true);
         }
         free(keyname);
@@ -718,7 +726,8 @@ void TizenWindowTcoreWl::RegisterEventHandlers() {
               self->input_method_context_->HandleTcoreWlEventKey(event, false);
         }
         if (!handled) {
-          self->view_delegate_->OnKey(keyname, keysymbol, compose, modifiers,
+          // See key-down handler for the keysymbol vs compose rationale.
+          self->view_delegate_->OnKey(keysymbol, compose, compose, modifiers,
                                       keycode, nullptr, false);
         }
         free(keyname);