RFR: 8325395: Missing copyright header in StackFilter.java

[Dmitry Cherepanov]

Adding missing copyright header to StackFilter.java and classpath exception paragraph to DeprecatedMethods.java/DeprecatedThing.java

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Commit messages:
 - 8325395: Missing copyright header in StackFilter.java

Changes: https://git.openjdk.org/jdk/pull/17821/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17821&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325395
  Stats: 31 lines in 3 files changed: 29 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/17821.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17821/head:pull/17821

PR: https://git.openjdk.org/jdk/pull/17821