Add support for more methods in TruncatingInputStream.

core-util/src/test/java/org/signal/core/util/InputStreamExtensionTests.kt

@@ -19,4 +19,20 @@ class InputStreamExtensionTests {
       assertEquals(bytes.size.toLong(), length)
     }
   }
+
+  @Test
+  fun `when I call readAtMostNBytes, I only read that many bytes`() {
+    val bytes = ByteArray(100)
+    val inputStream = bytes.inputStream()
+    val readBytes = inputStream.readAtMostNBytes(50)
+    assertEquals(50, readBytes.size)
+  }
+
+  @Test
+  fun `when I call readAtMostNBytes, it will return at most the length of the stream`() {
+    val bytes = ByteArray(100)
+    val inputStream = bytes.inputStream()
+    val readBytes = inputStream.readAtMostNBytes(200)
+    assertEquals(100, readBytes.size)
+  }
 }