Reset the baseline serialization test

We actually do have forwards and backwards serialization compatibility,
but the presence of instance field descriptors in the serialized form
confuse our testing approach.

Here's a manual test to show the compatibility.

```
$ qscala
Welcome to Scala 2.13.0-20180928-004946-4aa133f (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_172).
Type in expressions for evaluation. Or try :help.

scala> import java.util.Base64; def parseBase64Binary(s: String): Array[Byte] = Base64.getDecoder.decode(s); def printBase64Binary(data: Array[Byte]): String = Base64.getEncoder.encode(data).map(_.toChar).mkString; def serialize(o: AnyRef): String = {val bos = new java.io.ByteArrayOutputStream();val out = new java.io.ObjectOutputStream(bos);out.writeObject(o);out.flush();printBase64Binary(bos.toByteArray())}; def deserialize(string: String): AnyRef = {val bis = new java.io.ByteArrayInputStream(parseBase64Binary(string)); val in = new java.io.ObjectInputStream(bis); in.readObject()}; serialize(List);
warning: -nc is deprecated: scripts use cold compilation by default; use -Yscriptrunner for custom behavior
import java.util.Base64
parseBase64Binary: (s: String)Array[Byte]
printBase64Binary: (data: Array[Byte])String
serialize: (o: AnyRef)String
deserialize: (string: String)AnyRef
res0: String = rO0ABXNyACBzY2FsYS5jb2xsZWN0aW9uLmltbXV0YWJsZS5MaXN0JAAAAAAAAAADAwAAeHB4
```

```
scala> deserialize("rO0ABXNyACBzY2FsYS5jb2xsZWN0aW9uLmltbXV0YWJsZS5MaXN0JAAAAAAAAAADAwABTAARcGFydGlhbE5vdEFwcGxpZWR0ABFMc2NhbGEvRnVuY3Rpb24xO3hweA")
warning: -nc is deprecated: scripts use cold compilation by default; use -Yscriptrunner for custom behavior
res2: AnyRef = scala.collection.immutable.List$@a9f023e
$ scala-ref 2.13.x
Welcome to Scala 2.13.0-20180927-195543-c277d7d (OpenJDK 64-Bit Server VM, Java 1.8.0-adoptopenjdk).
Type in expressions for evaluation. Or try :help.

scala> import java.util.Base64; def parseBase64Binary(s: String): Array[Byte] = Base64.getDecoder.decode(s); def printBase64Binary(data: Array[Byte]): String = Base64.getEncoder.encode(data).map(_.toChar).mkString; def serialize(o: AnyRef): String = {val bos = new java.io.ByteArrayOutputStream();val out = new java.io.ObjectOutputStream(bos);out.writeObject(o);out.flush();printBase64Binary(bos.toByteArray())}; def deserialize(string: String): AnyRef = {val bis = new java.io.ByteArrayInputStream(parseBase64Binary(string)); val in = new java.io.ObjectInputStream(bis); in.readObject()}; serialize(List);
import java.util.Base64
parseBase64Binary: (s: String)Array[Byte]
printBase64Binary: (data: Array[Byte])String
serialize: (o: AnyRef)String
deserialize: (string: String)AnyRef
res0: String = rO0ABXNyACBzY2FsYS5jb2xsZWN0aW9uLmltbXV0YWJsZS5MaXN0JAAAAAAAAAADAwABTAARcGFydGlhbE5vdEFwcGxpZWR0ABFMc2NhbGEvRnVuY3Rpb24xO3hweA==

scala> deserialize("rO0ABXNyACBzY2FsYS5jb2xsZWN0aW9uLmltbXV0YWJsZS5MaXN0JAAAAAAAAAADAwAAeHB4")
res2: AnyRef = scala.collection.immutable.List$@595f9916
```

Author: retronym