Add backwards compatible implementation of overrideActivityTransition() (#4408)

This pull request adds `overrideActivityTransitionCompat()`, a
backwards-compatible version of `Activity.overrideActivityTransition()`
to be called in `Activity.onCreate()` in all Android versions.

This avoids duplicating the transition logic in different places of the
app to support older Android versions (in the activity launching code,
in `Activity.onCreate()` or in `Activity.finish()`).

- On API 34+, the implementation simply delegates to
`Activity.overrideActivityTransition()`.
- On API < 34, the implementation calls
`Activity.overridePendingTransition()` either immediately (opening
transition) or schedules it to be called later when the Activity is
finishing (closing transition).
- Rename `ActivityExensions.kt` to `ActivityExtensions.kt` (fix typo).

app/src/main/java/com/keylesspalace/tusky/MainActivity.kt

@@ -102,16 +102,17 @@ import com.keylesspalace.tusky.pager.MainPagerAdapter
 import com.keylesspalace.tusky.settings.PrefKeys
 import com.keylesspalace.tusky.usecase.DeveloperToolsUseCase
 import com.keylesspalace.tusky.usecase.LogoutUsecase
+import com.keylesspalace.tusky.util.ActivityConstants
 import com.keylesspalace.tusky.util.ShareShortcutHelper
 import com.keylesspalace.tusky.util.deleteStaleCachedMedia
 import com.keylesspalace.tusky.util.emojify
 import com.keylesspalace.tusky.util.getDimension
 import com.keylesspalace.tusky.util.getParcelableExtraCompat
 import com.keylesspalace.tusky.util.hide
+import com.keylesspalace.tusky.util.overrideActivityTransitionCompat
 import com.keylesspalace.tusky.util.reduceSwipeSensitivity
 import com.keylesspalace.tusky.util.show
 import com.keylesspalace.tusky.util.startActivityWithSlideInAnimation
-import com.keylesspalace.tusky.util.supportsOverridingActivityTransitions
 import com.keylesspalace.tusky.util.unsafeLazy
 import com.keylesspalace.tusky.util.viewBinding
 import com.mikepenz.iconics.IconicsDrawable
@@ -216,8 +217,12 @@ class MainActivity : BottomSheetActivity(), ActionButtonActivity, HasAndroidInje
         val activeAccount = accountManager.activeAccount
             ?: return // will be redirected to LoginActivity by BaseActivity
 
-        if (supportsOverridingActivityTransitions() && explodeAnimationWasRequested()) {
-            overrideActivityTransition(OVERRIDE_TRANSITION_OPEN, R.anim.explode, R.anim.activity_open_exit)
+        if (explodeAnimationWasRequested()) {
+            overrideActivityTransitionCompat(
+                ActivityConstants.OVERRIDE_TRANSITION_OPEN,
+                R.anim.explode,
+                R.anim.activity_open_exit
+            )
         }
 
         var showNotificationTab = false
@@ -988,10 +993,6 @@ class MainActivity : BottomSheetActivity(), ActionButtonActivity, HasAndroidInje
         }
         startActivity(intent)
         finish()
-        if (!supportsOverridingActivityTransitions()) {
-            @Suppress("DEPRECATION")
-            overridePendingTransition(R.anim.explode, R.anim.activity_open_exit)
-        }
     }
 
     private fun logout() {