RFR: 6864: Schema definition doesn't have optional ReturnValue "name" property

[Jessye Coleman-Shapiro]

This patch adds an optional return value "name" property to the Agent schema.  You are currently able to add this
"name" property to your event probe, however, adding it to the schema was missed in the reviewing process of
[JMC-6725](https://bugs.openjdk.java.net/browse/JMC-6725).

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Commit messages:
 - Add optional return value name property

Changes: https://git.openjdk.java.net/jmc/pull/94/files
 Webrev: https://webrevs.openjdk.java.net/jmc/94/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6864
  Stats: 2 lines in 2 files changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jmc/pull/94.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/94/head:pull/94

PR: https://git.openjdk.java.net/jmc/pull/94