RFR: 8260341: CDS dump VM init code does not check exceptions

[Ioi Lam]

When CDS dumping is enabled, special initialization happens during VM init. However, many of these calls do not properly check for exception. Instead, they rely on the implicit knowledge that `metaspace::allocate()` will exit the VM when allocation fails during CDS dumping. This makes the code hard to understand and tightly coupled to `metaspace::allocate()`.

The fix is: all code that makes allocation should be using CHECK macros, so each block of code can be individually understood without considering the behavior of `metaspace::allocate()`.

I added `TRAPS` to a bunch of CDS-related functions that are called during VM init. In some cases, I changed `Thread* THREAD` to `TRAPS`. This also eliminated a few `Thread* THREAD = Thread::current()` calls.

The "root" of these calls, such as `MetaspaceShared::prepare_for_dumping()`, now follows this pattern:

  EXCEPTION_MARK;
  ClassLoader::initialize_shared_path(THREAD);
  if (HAS_PENDING_EXCEPTION) {
    java_lang_Throwable::print(PENDING_EXCEPTION, tty);
    vm_exit_during_initialization("ClassLoader::initialize_shared_path() failed unexpectedly");
  }

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Commit messages:
 - 8260341: CDS dump VM init code does not check exceptions

Changes: https://git.openjdk.java.net/jdk/pull/2494/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2494&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260341
  Stats: 97 lines in 12 files changed: 18 ins; 11 del; 68 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2494.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2494/head:pull/2494

PR: https://git.openjdk.java.net/jdk/pull/2494