Fix some inspector action buttons not updating icon when theme changes

[timothyqiu]

This PR adds a EditorInspectorActionButton class to replace create_inspector_action_button(). Thus action button users don't have to add icon updating logic on-site.

[lodetrick]

If the point of this is to update the icon automatically, it could make sense to have the p_text argument be optional so you can create a button with just an icon.

[timothyqiu]

@lodetrick There is no such use case of inspector action button in the editor codebase.

[timothyqiu]

Updated to use TTRC() for button text.

The only exception is this one, I did not add NOTIFICATION_TRANSLATION_CHANGED because usually auto-translation won't take place for this property editor.

godot/editor/plugins/font_config_plugin.cpp

Lines 295 to 303 in 2cd3957

	if (script_editor) {
	// This property editor is currently only used inside the font import settings dialog.
	// Usually, the dialog needs to be closed in order to change the editor's language.
	// So we can ignore the auto-translation here.
	// TRANSLATORS: Script refers to a writing system.
	button_add = memnew(EditorInspectorActionButton(TTR("Add Script", "Locale"), SNAME("Add")));
	button_add->set_auto_translate_mode(AUTO_TRANSLATE_MODE_DISABLED);
	} else {