Support `toolkit-theme-set-functions' on Android and execute hooks safely

* java/org/gnu/emacs/EmacsNative.java (setEmacsParams): New arg
UIMODE.
(sendConfigurationChanged): New args DETAIL and UI_MODE.

* java/org/gnu/emacs/EmacsNoninteractive.java (main1): Provide
an undefined UI mode.

* java/org/gnu/emacs/EmacsService.java (EmacsService): New field
uiMode.
(onCreate): Initialize this field at start-up and provide the
same to setEmacsParams.
(onConfigurationChanged): If the UI mode has been altered,
generate a configuration changed event to match.

* src/android.c (android_ui_mode): New variable.
(setEmacsParams): New argument UI_MODE.  Initialize the same
from this variable.

* src/androidgui.h (enum android_configuration_changed): New
enum.
(struct android_configuration_changed_event): New field
`DETAIL'.  Convert fields providing specifics into a union of
display density information and a UI mode integer.

* src/androidterm.c (handle_one_android_event): Handle both
manners of configuration change events.
(android_term_init): Initialize Vtoolkit_theme from UI mode
provided at start-up.

* src/frame.c (syms_of_frame): Always define Vtoolkit_theme.
Define Qtoolkit_theme_set_functions.

* src/gtkutil.c (xg_update_dark_mode_for_all_displays):

* src/w32term.c (w32_read_socket): Generate special toolkit
theme events, rather than executing hooks directly within the
read_socket callback.

* src/keyboard.c (kbd_buffer_get_event)
<TOOLKIT_THEME_CHANGED_EVENT>: Run Qtoolkit_theme_set_functions
and set Vtoolkit_theme from event->ie.arg.

* src/termhooks.h (enum event_kind): New event
TOOLKIT_THEME_CHANGED_EVENT.

java/org/gnu/emacs/EmacsNoninteractive.java

@@ -67,7 +67,7 @@ public final class EmacsNoninteractive
     cacheDir = context.getCacheDir ().getCanonicalPath ();
     EmacsNative.setEmacsParams (assets, filesDir,
 				libDir, cacheDir, 0.0f,
-				0.0f, 0.0f, null, null,
+				0.0f, 0.0f, 0x0, null, null,
 				Build.VERSION.SDK_INT);
 
     /* Now find the dump file that Emacs should use, if it has already