console.lua: flush keybinds before sending mp.input opened events

This commit uses the undocumented `mp.flush_keybindings()` method
to ensure that all `console.lua` keybinds are set before
sending the `opened` event to `mp.input` clients.

Previously, the keybinds would only be flushed when `console.lua` went
idle. As the `opened` event is sent before this happens, clients
processing the event may end up flushing their own keybinds before this
happens. This makes it unreliable to use the `opened` event to override
keybinds set by `console.lua`; for example, adding different
behaviour to `input.select` when using `Shift+Enter` instead of `Enter`.

This commit allows the `opened` callback to be used to safely override
`console.lua` keybinds.

.luacheckrc: move flush_keybindings to globals

.luacheckrc

@@ -57,6 +57,7 @@ local mp_globals = {
             disable_key_bindings = {},
             enable_key_bindings = {},
             find_config_file = {},
+            flush_keybindings = {},
             format_time = {},
             get_mouse_pos = {},
             set_key_bindings = {},
@@ -78,7 +79,6 @@ local mp_internal = {
             UNKNOWN_TYPE = { fields = { info = {}, type = {} }},
             _legacy_overlay = { fields = { res_x = {}, res_y = {}, data = {}, update = {} }},
             cancel_timer = {},
-            flush_keybindings = {},
             get_osd_margins = {},
             input_define_section = {},
             input_disable_section = {},

player/lua/console.lua

@@ -1730,6 +1730,10 @@ mp.register_script_message("get-input", function (args)
     end
 
     set_active(true)
+
+    -- We want to ensure the keybindings have been set before sending the "opened" event
+    -- in case scripts want to override our bindings.
+    mp.flush_keybindings()
     mp.commandv("script-message-to", input_caller, input_caller_handler, "opened")
 end)