RFR: 8346572: Check is_reserved() before using ReservedSpace instances

[Stefan Karlsson]

There are a number of places where we reserve memory and create a ReservedSpace, and after the use the created instance without checking if the memory actually got reserved and the instance got initialized. This mostly affects code paths during JVM initialization and fixing this will mostly give better error handling and tracing.

The patch also includes some minor restructuring to get early returns and remove redundant null checks after calls to new.

Tested tier1 and GHA, but will run more tests when/if this gets accepted.

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Commit messages:
 - 8346572: Check is_reserved() before using ReservedSpace instances

Changes: https://git.openjdk.org/jdk/pull/22825/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22825&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346572
  Stats: 117 lines in 10 files changed: 47 ins; 31 del; 39 mod
  Patch: https://git.openjdk.org/jdk/pull/22825.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22825/head:pull/22825

PR: https://git.openjdk.org/jdk/pull/22825