fix: KeyboardToolbar in Modal on Android (#590)

## 📜 Description

Fixed a problem of non-working `KeyboardToolbar` functionality inside of
`Modal` on Android.

## 💡 Motivation and Context

The problem comes from the fact, that `Modal` on Android lives in their
own `window` hierarchy and as a result `activity?.currentFocus` is
always `null` (`currentFocus` is `null`).

A similar fix was added to iOS in this
[commit](22babd2).
On iOS the problem was in fact that we can not retrieve focused input if
keyboard is dismissed (unlike Android, because on Android the view still
in focus and carret is blinking after even keyboard dismissal). So on
Android it was harder to notice that bug (especially when `Modal`s
weren't officially supported).

So the fix with replacing `.currentFocus` with
`FocusedInputHolder.get()` seems to be pretty reliable, because our
`FocusedInputHolder` will always hold a reference to currently focused
input (doesn't matter which window contains that input, because we
attach `OnGlobalFocusChangeListener` to every window).

## 📢 Changelog

<!-- High level overview of important changes -->
<!-- For example: fixed status bar manipulation; added new types
declarations; -->
<!-- If your changes don't affect one of platform/language below - then
remove this platform/language -->

### Android

- replace `activity?.currentFocus` with `FocusedInputHolder.get()`;

## 🤔 How Has This Been Tested?

Tested manually on Pixel 3A (API 33, emulator).

## 📸 Screenshots (if appropriate):

|Before|After|
|-------|-----|
|<video
src="https://github.com/user-attachments/assets/f9390eed-f5cb-4e3d-840a-716399527b0b">|<video
src="https://github.com/user-attachments/assets/5232d81f-8020-4e9f-a8d1-d145d33d71f1">|

## 📝 Checklist

- [x] CI successfully passed
- [x] I added new mocks and corresponding unit-tests if library API was
changed

android/src/main/java/com/reactnativekeyboardcontroller/modules/KeyboardControllerModuleImpl.kt

@@ -22,10 +22,10 @@ class KeyboardControllerModuleImpl(private val mReactContext: ReactApplicationCo
 
   fun dismiss() {
     val activity = mReactContext.currentActivity
-    val view: View? = activity?.currentFocus
+    val view: View? = FocusedInputHolder.get()
 
     if (view != null) {
-      val imm = activity.getSystemService(Context.INPUT_METHOD_SERVICE) as? InputMethodManager
+      val imm = activity?.getSystemService(Context.INPUT_METHOD_SERVICE) as? InputMethodManager
       imm?.hideSoftInputFromWindow(view.windowToken, 0)
     }
   }
@@ -35,8 +35,7 @@ class KeyboardControllerModuleImpl(private val mReactContext: ReactApplicationCo
       return FocusedInputHolder.focus()
     }
 
-    val activity = mReactContext.currentActivity
-    val view: View? = activity?.currentFocus
+    val view: View? = FocusedInputHolder.get()
 
     if (view != null) {
       ViewHierarchyNavigator.setFocusTo(direction, view)