[jdk17] RFR: 8269543: The warning for System::setSecurityManager should only appear once for each caller

[Weijun Wang]

Add a cache to record which source has called `System::setSecurityManager` and only print out warning lines once for each.

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Commit messages:
 - renaming variables, two callers in test
 - one warning for each caller

Changes: https://git.openjdk.java.net/jdk17/pull/166/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17&pr=166&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269543
  Stats: 47 lines in 2 files changed: 34 ins; 0 del; 13 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/166.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/166/head:pull/166

PR: https://git.openjdk.java.net/jdk17/pull/166