RFR: 8282536: java.net.InetAddress should be a sealed class [v3]

[Aleksei Efimov]

> The following fix seals the `java.net.InetAddress` class and permits only two implementations - `java.net.Inet4Address` and `java.net.Inet6Address`. 
> 
> No issues have been detected by regression and JCK tests.
> 
> Links: [JBS](https://bugs.openjdk.java.net/browse/JDK-8282536) [CSR](https://bugs.openjdk.java.net/browse/JDK-8282880)

Aleksei Efimov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge branch 'master' into JDK-8282536_Seal_InetAddress
 - Cleanup unnessecary class loader checks, remove readObjectNoData
 - Add qualified Serializable usage with import
 - 8282536: java.net.InetAddress should be a sealed class

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7789/files
  - new: https://git.openjdk.java.net/jdk/pull/7789/files/f6901f09..44e6ab12

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7789&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7789&range=01-02

  Stats: 10743 lines in 405 files changed: 6113 ins; 2397 del; 2233 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7789.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7789/head:pull/7789

PR: https://git.openjdk.java.net/jdk/pull/7789