Use Compose for Library screen (#7557)

- Move Pager to Compose
- Move AppBar to Compose
- Use Stable interface for state
- Use pills for no. of manga in category instead of (x)

app/src/main/java/eu/kanade/presentation/library/LibraryState.kt

@@ -0,0 +1,32 @@
+package eu.kanade.presentation.library
+
+import androidx.compose.runtime.Stable
+import androidx.compose.runtime.derivedStateOf
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
+import eu.kanade.domain.category.model.Category
+import eu.kanade.tachiyomi.data.database.models.LibraryManga
+
+@Stable
+interface LibraryState {
+    val isLoading: Boolean
+    val categories: List<Category>
+    var searchQuery: String?
+    val selection: List<LibraryManga>
+    val selectionMode: Boolean
+    var hasActiveFilters: Boolean
+}
+
+fun LibraryState(): LibraryState {
+    return LibraryStateImpl()
+}
+
+class LibraryStateImpl : LibraryState {
+    override var isLoading: Boolean by mutableStateOf(true)
+    override var categories: List<Category> by mutableStateOf(emptyList())
+    override var searchQuery: String? by mutableStateOf(null)
+    override var selection: List<LibraryManga> by mutableStateOf(emptyList())
+    override val selectionMode: Boolean by derivedStateOf { selection.isNotEmpty() }
+    override var hasActiveFilters: Boolean by mutableStateOf(false)
+}