RFR: 4167: "Copy Column Headers" in stack trace view has no effect

[Jean-Philippe Bempel]

Add explicitly header column names as ILabelProvider does not provide this information

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Commit messages:
 - 4167: "Copy Column Headers" in stack trace view has no effect

Changes: https://git.openjdk.java.net/jmc/pull/198/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=198&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-4167
  Stats: 21 lines in 2 files changed: 16 ins; 1 del; 4 mod
  Patch: https://git.openjdk.java.net/jmc/pull/198.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/198/head:pull/198

PR: https://git.openjdk.java.net/jmc/pull/198