Introduce Hilt dependency injection

Uses Hilt to get the database initialization off of the
main thread.

The initial introduction always has a disproportionate
fan-out of boilerplate. In this case, all entry points which
were using UIViewModel needed to be annotated in order to let
the code gen know that they needed to support it.

The PacketRepository is injected into things via the main
thread (e.g., the MeshService) but due to the lazy declaration,
the database isn't hydrated until the DAO is access while on an
IO thread.

app/src/main/java/com/geeksville/mesh/database/MeshtasticDatabase.kt

@@ -1,8 +1,6 @@
 package com.geeksville.mesh.database
 
-import android.content.Context
 import androidx.room.Database
-import androidx.room.Room
 import androidx.room.RoomDatabase
 import com.geeksville.mesh.database.dao.PacketDao
 import com.geeksville.mesh.database.entity.Packet
@@ -10,27 +8,4 @@ import com.geeksville.mesh.database.entity.Packet
 @Database(entities = [Packet::class], version = 1, exportSchema = false)
 abstract class MeshtasticDatabase : RoomDatabase() {
     abstract fun packetDao(): PacketDao
-
-    companion object {
-        @Volatile
-        private var INSTANCE: MeshtasticDatabase? = null
-
-        fun getDatabase(
-            context: Context
-        ): MeshtasticDatabase {
-            return INSTANCE ?: synchronized(this) {
-                val instance = Room.databaseBuilder(
-                    context.applicationContext,
-                    MeshtasticDatabase::class.java,
-                    "meshtastic_database"
-                )
-                    .fallbackToDestructiveMigration()
-                    .build()
-                INSTANCE = instance
-
-                instance
-            }
-        }
-    }
-
 }