SI-8576 Temporarily disable part of serialization test

Parts of this test fail if testing a library built with -Xcheckinit.

The failures seem to be in two categories:

  - A component of the serialized structure does not have a
    declared SerialVersionUID, meaning that the extra field
    added to track initialization results in a different ID.
    This manifests as a `java.io.InvalidClassException` when
    deserializing the blobs of data saved in the test case.
  - Spurious `UnitializedFieldErrors` when calling methods on
    the object that has been serialized and then deserialized.

Until we figure out the right course of action (more @SerialVersionUID
annotations / weaker tests / ...), this commit disabled those tests.

Review by @lrytz