Tab swiping (#5408)

Task/Issue URL:
https://app.asana.com/0/1207418217763355/1209006734942815/f

### Description

This PR includes the complete implementation of the tab-swiping
functionality.

### Steps to test this PR

**Make sure you’ve completed the onboarding!**

#### New tab from long press
- [x] Long press on a tabs button
- [x] Verify a new tab is opened

#### New tab from the menu
- [x] Tap on the New tab menu item
- [x] Verify a new tab is opened

#### New tab from tab switcher
- [x] Go to tab switcher
- [x] Tap on the New tab button
- [x] Verify a new tab is opened

#### New tab recreation
- [x] Open a few tabs
- [x] Go to the tab switcher
- [x] Add a new tab
- [x] Verify a new tab is correctly displayed
- [x] Go back to the tab switcher
- [x] Close the NTP
- [x] Tap on the new tab button
- [x] Verify the new tab is correctly opened

#### Swiping position
- [x] Open at least 3 tabs
- [x] Select the 1st one in the tab switcher
- [x] Swipe to the last one
- [x] Go to tab switcher and verify the correct tab is selected
- [x] Tap on the 2nd tab
- [x] Verify the correct tab is opened

#### New link
- [x] Open any website
- [x] Long press on a link to open in new tab
- [x] Verify the link is opened in a new tab

#### New link in the background
- [x] Open any website
- [x] Long press on a link to open in background tab
- [x] Verify the link is opened in a new tab in the background

#### New link in the background
- [x] Make sure the DDG app is the default browser app
- [x] Open an app that can open links in custom tabs (i.e. Twitter,
Facebook)
- [x] Open a link in a custom tab
- [x] Verify the link opens correctly
- [x] Move the tab to the app
- [x] Verify the tab is correctly displayed within the app

#### Switch to tab
- [x] Start typing a site address that’s already opened in another tab
- [x] Tap on the “Switch to tab” item
- [x] Verify the existing tab with the link is shown instead of opening
a new tab

#### Changing the omnibar position
- [x] Open a few tabs
- [x] Go to settings and change the omnibar position
- [x] The app will reload (the cached sites are cleared)
- [x] Swipe through the tabs and verify the load correctly

#### Bookmarks
- [x] Load a site
- [x] Add it to the boorkmarks
- [x] Open a different tab
- [x] Go to Bookmarks and select the saved boormark
- [x] Verify the bookmark loads correctly

#### Default site
- [x] Set some default URL in Settings -> General -> Show on App Launch
- [x] Kill the app and relaunch it
- [x] Verify the default site is correctly loaded in a new tab
- [x] Kill the app and relaunch it
- [x] Verify the default site is loaded in the same tab as before (no
new tab is added)

---------

Co-authored-by: Noelia Alcala <nalcalag@gmail.com>

Author: 0nko

app/src/androidTest/java/com/duckduckgo/app/browser/BrowserTabViewModelTest.kt

@@ -503,13 +503,18 @@ class BrowserTabViewModelTest {
     private val mockBrokenSitePrompt: BrokenSitePrompt = mock()
     private val mockTabStatsBucketing: TabStatsBucketing = mock()
     private val mockDuckChatJSHelper: DuckChatJSHelper = mock()
+    private val swipingTabsFeature = FakeFeatureToggleFactory.create(SwipingTabsFeature::class.java)
+    private val swipingTabsFeatureProvider = SwipingTabsFeatureProvider(swipingTabsFeature)
 
     private val defaultBrowserPromptsExperimentShowPopupMenuItemFlow = MutableStateFlow(false)
     private val mockDefaultBrowserPromptsExperiment: DefaultBrowserPromptsExperiment = mock()
 
     @Before
     fun before() = runTest {
         MockitoAnnotations.openMocks(this)
+
+        swipingTabsFeature.self().setRawStoredState(State(enable = true))
+
         db = Room.inMemoryDatabaseBuilder(context, AppDatabase::class.java)
             .allowMainThreadQueries()
             .build()
@@ -680,6 +685,7 @@ class BrowserTabViewModelTest {
             tabStatsBucketing = mockTabStatsBucketing,
             maliciousSiteBlockerWebViewIntegration = mock(),
             defaultBrowserPromptsExperiment = mockDefaultBrowserPromptsExperiment,
+            swipingTabsFeature = swipingTabsFeatureProvider,
         )
 
         testee.loadData("abc", null, false, false)
@@ -2325,14 +2331,29 @@ class BrowserTabViewModelTest {
     }
 
     @Test
-    fun whenUserRequestedToOpenNewTabThenNewTabCommandIssued() {
+    fun whenUserRequestedToOpenNewTabAndNoEmptyTabExistsThenNewTabCommandIssued() {
+        tabsLiveData.value = listOf(TabEntity("1", "https://example.com", position = 0))
         testee.userRequestedOpeningNewTab()
         verify(mockCommandObserver, atLeastOnce()).onChanged(commandCaptor.capture())
         val command = commandCaptor.lastValue
         assertTrue(command is Command.LaunchNewTab)
         verify(mockPixel, never()).fire(AppPixelName.TAB_MANAGER_NEW_TAB_LONG_PRESSED)
     }
 
+    @Test
+    fun whenUserRequestedToOpenNewTabAndEmptyTabExistsThenSelectTheEmptyTab() = runTest {
+        val emptyTabId = "EMPTY_TAB"
+        whenever(mockTabRepository.flowTabs).thenReturn(flowOf(listOf(TabEntity(emptyTabId))))
+        testee.userRequestedOpeningNewTab()
+
+        verify(mockCommandObserver, atLeastOnce()).onChanged(commandCaptor.capture())
+        val command = commandCaptor.lastValue
+        assertFalse(command is Command.LaunchNewTab)
+
+        verify(mockTabRepository).select(emptyTabId)
+        verify(mockPixel, never()).fire(AppPixelName.TAB_MANAGER_NEW_TAB_LONG_PRESSED)
+    }
+
     @Test
     fun whenUserRequestedToOpenNewTabByLongPressThenPixelFired() {
         testee.userRequestedOpeningNewTab(longPress = true)