RFR: 8284640: CollectorImpl class could be a record class

[altrisi]

Changes the definition of `CollectorImpl` to be a record.

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Commit messages:
 - Remove explicit `static` modifier
 - 8284640: CollectorImpl class could be a record class

Changes: https://git.openjdk.java.net/jdk/pull/8179/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8179&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284640
  Stats: 43 lines in 1 file changed: 0 ins; 37 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8179.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8179/head:pull/8179

PR: https://git.openjdk.java.net/jdk/pull/8179