[SB Refactor] Use the calculated mobileIsDefault for failed connection.

This is not directly related to b/225902574 but I noticed it while
looking at that issue.

In the case where carrier merged comes through a WIFI connection, it
would never show the ! because mobileIsDefault=false. However, the
carrier merged connection could be non-validated, in which case we
*should* show the ! (but wouldn't right now).

This CL updates the `isDefaultConnectionFailed` calculation to also
show the ! if carrier merged is default and not validated. It does this
by using the interactor's interally calculated `mobileIsDefault` flow,
which includes carrier merged (as opposed to the repo's
`mobileIsDefault` flow, which does not include carrier merged).

Bug: 225902574
Test: atest MobileIconsInteractorTest
Change-Id: Ic79cc1755a67400de067a51abcf654b1294b7fe1

packages/SystemUI/src/com/android/systemui/statusbar/pipeline/mobile/domain/interactor/MobileIconsInteractor.kt

@@ -259,7 +259,7 @@ constructor(
      */
     override val isDefaultConnectionFailed: StateFlow<Boolean> =
         combine(
-                mobileConnectionsRepo.mobileIsDefault,
+                mobileIsDefault,
                 mobileConnectionsRepo.defaultConnectionIsValidated,
                 forcingCellularValidation,
             ) { mobileIsDefault, defaultConnectionIsValidated, forcingCellularValidation ->

packages/SystemUI/tests/src/com/android/systemui/statusbar/pipeline/mobile/domain/interactor/MobileIconsInteractorTest.kt

@@ -361,6 +361,21 @@ class MobileIconsInteractorTest : SysuiTestCase() {
             job.cancel()
         }
 
+    @Test
+    fun failedConnection_carrierMergedDefault_notValidated_failed() =
+        testScope.runTest {
+            var latest: Boolean? = null
+            val job = underTest.isDefaultConnectionFailed.onEach { latest = it }.launchIn(this)
+
+            connectionsRepository.hasCarrierMergedConnection.value = true
+            connectionsRepository.defaultConnectionIsValidated.value = false
+            yield()
+
+            assertThat(latest).isTrue()
+
+            job.cancel()
+        }
+
     /** Regression test for b/275076959. */
     @Test
     fun failedConnection_dataSwitchInSameGroup_notFailed() =