RFR: 8273101: Eliminate the usage of threadgroup sandboxing in the java.util.logging [v2]

[Sergey Bylokhov]

> At the time Java supported applets and webstart, a special mechanism for launching various applications in one JVM was used to reduce memory usage and each application was isolated from each other.
> 
> This isolation was implemented via ThreadGroups where each application created its own thread group and all data for the application was stored in the context of its own group.
> 
> Some parts of the JDK used ThreadGroups directly, others used special classes like sun.awt.AppContext.
> 
> Such sandboxing became useless since the plugin and webstart are no longer supported and were removed in jdk11.
> 
> Note that this is just a first step for the overall cleanup, here is my plan:
> 1. Cleanup the usage of AppContext in the “java.util.logging.LogManager" class in the java.base module.
> 2. Cleanup the usage of TheadGroup in the JavaSound
> 3. Cleanup the usage of TheadGroup in the JavaBeans
> 4. Cleanup the usage of AppContext in the Swing
> 5. Cleanup the usage of AppContext in the AWT
> 6. Delete the AppContext class.
> 
> The current PR is for the first step. So this is the request to delete the usage of AppContext in the LogManager and related tests.
> 
> Tested by tier1/tier2/tier3 and jdk_desktop tests.

Sergey Bylokhov has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Merge branch 'master' into JDK-8273101
 - Some tests deleted
 - Update the RootLevelInConfigFile test
 - Initial version of JDK-8273101

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Changes: https://git.openjdk.java.net/jdk/pull/5326/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5326&range=01
  Stats: 1423 lines in 10 files changed: 0 ins; 1418 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5326.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5326/head:pull/5326

PR: https://git.openjdk.java.net/jdk/pull/5326