Fix mouse mode bindings with multiple actions

The following config was broken:
```
  [mouse]
  bindings = [
  { mouse = "Right", mods = "Shift", action = "Copy"            },
  { mouse = "Right", mods = "Shift", action = "ClearSelection"  },
  ]
```

Only the first action was applied. Change to allow more than one exact
match in mouse mode with shift held, but keep the logic to not allow
fallback search if any exact match was found.

Fixes: 1a143d1 (Fix trigger of normal bindings in mouse mode)

alacritty/src/input/mod.rs

@@ -1004,17 +1004,18 @@ impl<T: EventListener, A: ActionContext<T>> Processor<T, A> {
         let mouse_bindings = self.ctx.config().mouse_bindings().to_owned();
 
         // If mouse mode is active, also look for bindings without shift.
-        let mut check_fallback = mouse_mode && mods.contains(ModifiersState::SHIFT);
+        let fallback_allowed = mouse_mode && mods.contains(ModifiersState::SHIFT);
+        let mut exact_match_found = false;
 
         for binding in &mouse_bindings {
             // Don't trigger normal bindings in mouse mode unless Shift is pressed.
-            if binding.is_triggered_by(mode, mods, &button) && (check_fallback || !mouse_mode) {
+            if binding.is_triggered_by(mode, mods, &button) && (fallback_allowed || !mouse_mode) {
                 binding.action.execute(&mut self.ctx);
-                check_fallback = false;
+                exact_match_found = true;
             }
         }
 
-        if check_fallback {
+        if fallback_allowed && !exact_match_found {
             let fallback_mods = mods & !ModifiersState::SHIFT;
             for binding in &mouse_bindings {
                 if binding.is_triggered_by(mode, fallback_mods, &button) {