RFR: 8261551: Remove special CDS handling in Metaspace::allocate

[Ioi Lam]

Please review this simple patch to remove the special handling of OOM conditions inside `Metaspace::allocate()` for CDS archive dumping. Now the OOM exception will be thrown normally and will be handled by `MetaspaceShared::preload_and_dump()` and `ClassListParser::parse()`.

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Commit messages:
 - 8261551: Remove special CDS handling in Metaspace::allocate

Changes: https://git.openjdk.java.net/jdk/pull/3185/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3185&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261551
  Stats: 9 lines in 2 files changed: 0 ins; 7 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3185.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3185/head:pull/3185

PR: https://git.openjdk.java.net/jdk/pull/3185