RFR: 8302491: NoClassDefFoundError omits the original cause of an error [v2]

[Ilarion Nakonechnyy]

> The proposed approach added a new function for getting the cause of an exception -`java_lang_Throwable::get_cause_simple `, that gets called within `InstanceKlass::add_initialization_error`  if an old one `java_lang_Throwable::get_cause_with_stack_trace` didn't succeed because of an exception during the VM call. The simple function doesn't call the VM for getting a stack trace but fills in any other information about an exception.
> 
> Besides that, the discovering information about an exception was added to `ConstantPoolCacheEntry::save_and_throw_indy_exc` function. 
> 
> Jtreg for reproducing the issue also was added to the commit. 
> The commit was tested with tier1 tests.

Ilarion Nakonechnyy has updated the pull request incrementally with two additional commits since the last revision:

 - Address review notes
 - Correct the jtreg test -
   check stacktrace only for NoClassDefFoundError

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/12566/files
  - new: https://git.openjdk.org/jdk/pull/12566/files/7ee0adbd..f2e5b362

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12566&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12566&range=00-01

  Stats: 15 lines in 4 files changed: 4 ins; 2 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/12566.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12566/head:pull/12566

PR: https://git.openjdk.org/jdk/pull/12566