RFR: 8252600: [JVMCI] update JVMCI code style and mx configuration

[Doug Simon]

This PR updates the configuration files used to develop the JVMCI Java and C++ sources with mx and Eclipse.

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Commit messages:
 - 8252600: [JVMCI] update JVMCI code style and mx configuration

Changes: https://git.openjdk.java.net/jdk/pull/3559/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3559&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252600
  Stats: 2096 lines in 14 files changed: 752 ins; 1344 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3559.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3559/head:pull/3559

PR: https://git.openjdk.java.net/jdk/pull/3559