[jdk18u] RFR: 8285517: System.getenv() returns unexpected value if environment variable has non ASCII character

[Ichiroh Takiguchi]

Backport JDK-8285517

Backport is not clean.
Because following patch is not integrated on test/jdk/java/lang/ProcessBuilder/Basic.java:
  8284161: Implementation of Virtual Threads (Preview)
The modification does not affect logic, just remove following line:
  import java.lang.reflect.Field;

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Commit messages:
 - Backport 890771e708277c5f7ea9460ff7bcc7e4cae87eab

Changes: https://git.openjdk.java.net/jdk18u/pull/139/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18u&pr=139&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285517
  Stats: 264 lines in 5 files changed: 217 ins; 24 del; 23 mod
  Patch: https://git.openjdk.java.net/jdk18u/pull/139.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18u pull/139/head:pull/139

PR: https://git.openjdk.java.net/jdk18u/pull/139