RFR: 8356893: Use "stdin.encoding" for reading System.in with InputStreamReader/Scanner

[Volkan Yazici]

There are several locations in the JDK source where `System.in` and `FileDescriptor.in` is read with `InputStreamReader` and `Scanner` using the default charset. As recommended by the recently merged [JDK-8356420](https://bugs.openjdk.org/browse/JDK-8356420), this PR replaces the default charset with the one provided by the `stdin.encoding` system property.

### Fixing strategy

* Where it is obvious that `System.in` is passed to `InputStreamReader`/`Scanner` ctors, `stdin.encoding` is employed fixed.
* Where the `InputStream` passed to `InputStreamReader`/`Scanner` ctors is difficult to determine if it can ever be `System.in`, `assert` expressions are placed.
* Where the odds of receiving `System.in` are low, yet it is technically possible (e.g., `Process::getInputStream`, `URL::openConnection`, `Class::getResourceAsStream`), nothing is done.

@naotoj was kind enough to guide me in this PR, and stated `assert` expressions can be skipped, since they are many ways one can circumvent those checks; wrapping `System.in`, usage of `System::setIn`, etc. Yet we decided to leave them as is to collect feedback from other reviewers too.

### Scanning strategy

The following ~alien technology~ advanced static analysis tools are used to scan the code for potentially affected places:


# Perl is used for multi-line matching
find . -name "*.java" -exec perl -0777 -ne 'my $r = (/(InputStreamReader|Scanner)(\s*System.in)/) ? 0 : 1; exit $r' {} ; -print
git grep -H 'FileDescriptor.in' "*.java"


All calls to `InputStreamReader::new` and `Scanner::new` are checked too.

### Problems encountered

1. Due to either irregular, or non-existent license header, could not update the copyright year for following classes:

    ```
    DOMImplementationRegistry 
    InputRC 
    ListingErrorHandler 
    PandocFilter 
    ```
2. Could not employ `stdin.encoding` in `PandocFilter`, since the bootstrap VM running that class returns empty for that system property

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

Commit messages:
 - Use `stdin.encoding` in `InputStreamReader` and `Scanner` instantiations

Changes: https://git.openjdk.org/jdk/pull/25368/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25368&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356893
  Stats: 244 lines in 58 files changed: 111 ins; 20 del; 113 mod
  Patch: https://git.openjdk.org/jdk/pull/25368.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25368/head:pull/25368

PR: https://git.openjdk.org/jdk/pull/25368