RFR: 8357996: Use "stdin.encoding" for reading System.in with InputStreamReader/Scanner [tools] [v3]

[Volkan Yazici]

> Passes the `Charset` read from the `stdin.encoding` system property while creating `InputStreamReader` or `Scanner` instances for `System.in`.
> 
> `stdin.encoding` is a recently added property for Java 25 in [JDK-8350703](https://bugs.openjdk.org/browse/JDK-8350703). Employing it throughout the entire code base is addressed by the parent ticket [JDK-8356893](https://bugs.openjdk.org/browse/JDK-8356893). JDK-8357996 this PR is addressing is a sub-task of JDK-8356893 and is concerned with only areas related to tools.

Volkan Yazici has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:

 - Merge remote-tracking branch 'upstream/master' into stdinEnc-build
 - Provide fallback for `stdin.encoding` in `ExternalEditor`
 - Discard changes unrelated with build and tools
 - Revert superfluous changes
   
   Remove assertion in `DOMImplementationRegistry`
 - Revert changes to 3rd parties in `com/sun/org/apache`
 - Revert `PandocFilter` changes
   
   `PandocFilter` et al. gets called using the boot JDK,
   which doesn't have `stdin.encoding` yet.
 - Use `stdin.encoding` in `InputStreamReader` and `Scanner` instantiations
   
   Improve `CharsetTest`

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Changes: https://git.openjdk.org/jdk/pull/25541/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25541&range=02
  Stats: 9 lines in 3 files changed: 2 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/25541.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25541/head:pull/25541

PR: https://git.openjdk.org/jdk/pull/25541