Replace java.time APIs with kotlin(x).(date)time (#3001)

* Replace java.time APIs with kotlin(x).(date)time

kotlinx-datetime explicitly says in its README that it does not cover
i18n, so we have to stick with using their toJavaX converters wherever
we localise dates and times.

Yes, some of these replacements are... questionable. But I wanted to
try and maximise the replacement for now.

* Bump kotlinx-datetime to 0.8.0

* More kotlin.time/kotlinx-datetime replacements

* Remove redundant init block & make attributes val

* Replace new use of java.time.Instant

app/src/main/java/mihon/feature/upcoming/UpcomingViewModel.kt

@@ -4,17 +4,20 @@ import androidx.compose.ui.util.fastMap
 import androidx.compose.ui.util.fastMapIndexedNotNull
 import androidx.lifecycle.viewModelScope
 import eu.kanade.core.util.insertSeparatorsReversed
-import eu.kanade.tachiyomi.util.lang.toLocalDate
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.YearMonth
+import kotlinx.datetime.toLocalDateTime
+import kotlinx.datetime.yearMonth
 import mihon.core.viewmodel.StateViewModel
 import mihon.domain.upcoming.interactor.GetUpcomingManga
 import tachiyomi.domain.manga.model.Manga
 import uy.kohesive.injekt.Injekt
 import uy.kohesive.injekt.api.get
-import java.time.LocalDate
-import java.time.YearMonth
+import kotlin.time.Clock
 
 class UpcomingViewModel(
     private val getUpcomingManga: GetUpcomingManga = Injekt.get(),
@@ -41,8 +44,14 @@ class UpcomingViewModel(
             .insertSeparatorsReversed { before, after ->
                 if (after != null) mangaCount++
 
-                val beforeDate = before?.manga?.expectedNextUpdate?.toLocalDate()
-                val afterDate = after?.manga?.expectedNextUpdate?.toLocalDate()
+                val beforeDate = before?.manga
+                    ?.expectedNextUpdate
+                    ?.toLocalDateTime(TimeZone.currentSystemDefault())
+                    ?.date
+                val afterDate = after?.manga
+                    ?.expectedNextUpdate
+                    ?.toLocalDateTime(TimeZone.currentSystemDefault())
+                    ?.date
 
                 if (beforeDate != afterDate && afterDate != null) {
                     UpcomingUIModel.Header(afterDate, mangaCount).also { mangaCount = 0 }
@@ -73,7 +82,10 @@ class UpcomingViewModel(
     }
 
     data class State(
-        val selectedYearMonth: YearMonth = YearMonth.now(),
+        val selectedYearMonth: YearMonth = Clock.System.now()
+            .toLocalDateTime(TimeZone.currentSystemDefault())
+            .date
+            .yearMonth,
         val items: List<UpcomingUIModel> = listOf(),
         val events: Map<LocalDate, Int> = mapOf(),
         val headerIndexes: Map<LocalDate, Int> = mapOf(),