Split Omnibar: Omnibar layout refactoring (#6983)

Task/Issue URL:
https://app.asana.com/1/137249556945/project/1207418217763355/task/1211565479656354

### Description

This PR refactors the `OmnibarLayout` and `SingleOmnibarLayout`.
`OmnibarLayout` was renamed to `LegacyOmnibarLayout` and a new
`OmnibarLayout` is a unified, merged version of `OmnibarLayout` and
`SingleOmnibarLayout`.

Thew new omnibar is guarded by a `useUnifiedOmnibarLayout` feature flag.
To make that work, an `OminbarView` interface needed to be extracted,
which is now used within the `Omnibar` class. Depending on the flag
value, either the old `LegacyOmnibarLayout ` or the new `OmnibarLayout`
is used. The feature flag is enabled by default.

Also, some of the interfaces from `OmnibarLayout` had to be extracted
(`StateChange`, `Decoration`) to avoid duplication.

### Steps to test this PR

_FF enabled_
- [x] Verify that onboarding highlighting works
- [x] Verify all buttons work
- [x] Verify tab swiping works
- [x] Verify tracker animations work
- [x] Verify the cookies animations work
- [x] Verify that omnibar hiding on scroll works

_FF disabled_
- [x] Disable the `useUnifiedOmnibarLayout` FF in the internal settings
- [x] Verify that onboarding highlighting works
- [x] Verify all buttons work
- [x] Verify tab swiping works
- [x] Verify tracker animations work
- [x] Verify the cookies animations work
- [x] Verify that omnibar hiding on scroll works

Author: 0nko

app/src/main/java/com/duckduckgo/app/browser/BrowserActivity.kt

@@ -767,7 +767,7 @@ open class BrowserActivity : DuckDuckGoActivity() {
             val anchorView =
                 when (settingsDataStore.omnibarPosition) {
                     TOP -> null
-                    BOTTOM -> currentTab?.getOmnibar()?.newOmnibar?.toolbar ?: binding.fragmentContainer
+                    BOTTOM -> currentTab?.getOmnibar()?.omnibarView?.toolbar ?: binding.fragmentContainer
                 }
             DefaultSnackbar(
                 parentView = binding.fragmentContainer,
@@ -868,7 +868,7 @@ open class BrowserActivity : DuckDuckGoActivity() {
             launchNewDuckChat(url, withTransition)
         }
 
-        currentTab?.getOmnibar()?.newOmnibar?.omnibarTextInput?.let {
+        currentTab?.getOmnibar()?.omnibarView?.omnibarTextInput?.let {
             hideKeyboard(it)
         }
     }

app/src/main/java/com/duckduckgo/app/browser/BrowserTabFragment.kt

@@ -143,7 +143,11 @@ import com.duckduckgo.app.browser.model.LongPressTarget
 import com.duckduckgo.app.browser.navigation.bar.view.BrowserNavigationBarObserver
 import com.duckduckgo.app.browser.newtab.NewTabPageProvider
 import com.duckduckgo.app.browser.omnibar.Omnibar
+import com.duckduckgo.app.browser.omnibar.Omnibar.FindInPageListener
+import com.duckduckgo.app.browser.omnibar.Omnibar.ItemPressedListener
+import com.duckduckgo.app.browser.omnibar.Omnibar.LogoClickListener
 import com.duckduckgo.app.browser.omnibar.Omnibar.OmnibarTextState
+import com.duckduckgo.app.browser.omnibar.Omnibar.TextListener
 import com.duckduckgo.app.browser.omnibar.Omnibar.ViewMode
 import com.duckduckgo.app.browser.omnibar.OmnibarItemPressedListener
 import com.duckduckgo.app.browser.omnibar.QueryOrigin
@@ -1012,7 +1016,11 @@ class BrowserTabFragment :
     override fun onActivityCreated(savedInstanceState: Bundle?) {
         super.onActivityCreated(savedInstanceState)
 
-        omnibar = Omnibar(settingsDataStore.omnibarPosition, binding)
+        omnibar = Omnibar(
+            omnibarPosition = settingsDataStore.omnibarPosition,
+            binding = binding,
+            isUnifiedOmnibarEnabled = androidBrowserConfigFeature.useUnifiedOmnibarLayout().isEnabled(),
+        )
 
         webViewContainer = binding.webViewContainer
         configureObservers()
@@ -1100,7 +1108,7 @@ class BrowserTabFragment :
 
     private fun configureLogoClickListener() {
         omnibar.configureLogoClickListener(
-            object : Omnibar.LogoClickListener {
+            object : LogoClickListener {
                 override fun onClick(url: String) {
                     viewModel.onDynamicLogoClicked(url)
                 }
@@ -2952,7 +2960,7 @@ class BrowserTabFragment :
 
     private fun configureFindInPage() {
         omnibar.configureFindInPage(
-            object : Omnibar.FindInPageListener {
+            object : FindInPageListener {
                 override fun onFocusChanged(
                     hasFocus: Boolean,
                     query: String,
@@ -2983,7 +2991,7 @@ class BrowserTabFragment :
 
     private fun configureItemPressedListener() {
         omnibar.configureItemPressedListeners(
-            object : Omnibar.ItemPressedListener {
+            object : ItemPressedListener {
                 override fun onTabsButtonPressed() {
                     this@BrowserTabFragment.onTabsButtonPressed()
                 }
@@ -3025,6 +3033,10 @@ class BrowserTabFragment :
                     val isNtp = omnibar.viewMode == ViewMode.NewTab
                     onOmnibarDuckChatPressed(query = omnibar.getText(), hasFocus = hasFocus, isNtp = isNtp)
                 }
+
+                override fun onBackButtonPressed() {
+                    hideKeyboard()
+                }
             },
         )
         omnibar.configureOmnibarItemPressedListeners(
@@ -3038,7 +3050,7 @@ class BrowserTabFragment :
 
     private fun configureOmnibarTextInput() {
         omnibar.addTextListener(
-            object : Omnibar.TextListener {
+            object : TextListener {
                 override fun onFocusChanged(
                     hasFocus: Boolean,
                     query: String,