RFR: 8377665: JFR: Symbol table not setup for early class unloading

[Joel Sikström]

Hello,

We observe a crash when running a major GC very early, which unloads classes, calling into JFR which is not properly set up for class unloading this early. A simple fix for this is to move the creation of the symbol table to the early setup of JFR, which allows us to successfully call `JfrCheckpointManager::on_unloading_classes()`.

Testing:
 * Crash reproducer no longer crashes
 * Running through Oracle's tier1-4

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Commit messages:
 - 8377665: JFR: Symbol table not setup for early class unloading

Changes: https://git.openjdk.org/jdk/pull/29672/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29672&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8377665
  Stats: 8 lines in 1 file changed: 5 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/29672.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29672/head:pull/29672

PR: https://git.openjdk.org/jdk/pull/29672