refactor: implement repository pattern for NodeDB (#835)

- enforce Unidirectional Data Flow removing nodeDB updates via `MainActivity`/`UIState`
- merge `MyNodeInfoDao` into `NodeInfoDao`
- move node list re-indexing to database

app/src/androidTest/java/com/geeksville/mesh/NodeInfoDaoTest.kt

@@ -0,0 +1,104 @@
+package com.geeksville.mesh
+
+import androidx.room.Room
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.platform.app.InstrumentationRegistry
+import com.geeksville.mesh.database.MeshtasticDatabase
+import com.geeksville.mesh.database.dao.NodeInfoDao
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.runBlocking
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class NodeDBTest {
+    private lateinit var database: MeshtasticDatabase
+    private lateinit var nodeInfoDao: NodeInfoDao
+
+    private val testNodeNoPosition = NodeInfo(
+        8,
+        MeshUser(
+            "+16508765308".format(8),
+            "Kevin MesterNoLoc",
+            "KLO",
+            MeshProtos.HardwareModel.ANDROID_SIM,
+            false
+        ),
+        null
+    )
+
+    private val myNodeInfo: MyNodeInfo = MyNodeInfo(
+        myNodeNum = testNodeNoPosition.num,
+        hasGPS = false,
+        model = null,
+        firmwareVersion = null,
+        couldUpdate = false,
+        shouldUpdate = false,
+        currentPacketId = 1L,
+        messageTimeoutMsec = 5 * 60 * 1000,
+        minAppVersion = 1,
+        maxChannels = 8,
+        hasWifi = false,
+        channelUtilization = 0f,
+        airUtilTx = 0f,
+    )
+
+    private val testPositions = arrayOf(
+        Position(32.776665, -96.796989, 35, 123), // dallas
+        Position(32.960758, -96.733521, 35, 456), // richardson
+        Position(32.912901, -96.781776, 35, 789), // north dallas
+    )
+
+    private val testNodes = listOf(testNodeNoPosition) + testPositions.mapIndexed { index, it ->
+        NodeInfo(
+            9 + index,
+            MeshUser(
+                "+165087653%02d".format(9 + index),
+                "Kevin Mester$index",
+                "KM$index",
+                MeshProtos.HardwareModel.ANDROID_SIM,
+                false
+            ),
+            it
+        )
+    }
+
+    @Before
+    fun createDb(): Unit = runBlocking {
+        val context = InstrumentationRegistry.getInstrumentation().targetContext
+        database = Room.inMemoryDatabaseBuilder(context, MeshtasticDatabase::class.java).build()
+        nodeInfoDao = database.nodeInfoDao()
+
+        nodeInfoDao.apply{
+            putAll(testNodes)
+            setMyNodeInfo(myNodeInfo)
+        }
+    }
+
+    @After
+    fun closeDb() {
+        database.close()
+    }
+
+    @Test // node list size
+    fun testNodeListSize() = runBlocking {
+        val nodes = nodeInfoDao.nodeDBbyNum().first()
+        assertEquals(nodes.size, 4)
+    }
+
+    @Test // nodeDBbyNum() re-orders our node at the top of the list
+    fun testOurNodeIntoIsFirst() = runBlocking {
+        val nodes = nodeInfoDao.nodeDBbyNum().first()
+        assertEquals(nodes.values.first(), testNodeNoPosition)
+    }
+
+    @Test // getNodeInto()
+    fun testGetNodeInto() = runBlocking {
+        for (node in nodeInfoDao.getNodes().first()) {
+            assertEquals(nodeInfoDao.getNodeInfo(node.num), node)
+        }
+    }
+}