RFR: JDK-8149138: [javadoc] Fix SerialFormBuilder eliminate String bashing

[Hannes Wallnöfer]

Removal of ugly old code in `SerializedFormBuilder.java`. Luckily there already is a clean overloaded method in the associated writer that we can use, so this is mostly a removal of code that is no longer used.

I also enhanced the test to cover more cases such as primitive arrays and linked references.

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Commit messages:
 - JDK-8149138: [javadoc] Fix SerialFormBuilder eliminate String bashing

Changes: https://git.openjdk.java.net/jdk/pull/4284/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4284&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8149138
  Stats: 95 lines in 5 files changed: 38 ins; 46 del; 11 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4284.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4284/head:pull/4284

PR: https://git.openjdk.java.net/jdk/pull/4284