RFR: 8313312: Add missing classpath exception copyright header

[Amit Kumar]

Adds `classpath exception` in multiple files, affects copyright header only.

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Commit messages:
 - adds classpath exception

Changes: https://git.openjdk.org/jdk/pull/15070/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15070&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313312
  Stats: 60 lines in 20 files changed: 40 ins; 0 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/15070.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15070/head:pull/15070

PR: https://git.openjdk.org/jdk/pull/15070