RFR: 8308764: Reporting errors from create_vm may crash [v2]

[David Holmes]

> There are more details in the bug report but the basic fix is to not delete the main_thread so that it is available to report the exception that caused VM initialization to fail. Added some additional comments too.
> 
> Testing:
>  - basic fault injection to test non-exception exit paths both before and after Universe:;is_fully_initialized() which exercises the failing use of JavaThread::current()
>  -  tiers 1-3 sanity testing
> 
> Thanks.

David Holmes has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:

 - Changes per Coleen's suggestion.
 - Changes per Coleen's suggestion.
 - Merge branch 'master' into 8308764-create_vm_errors
 - Fix indentation
 - Merge branch 'master' into 8308764-create_vm_errors
 - Fixed typo
 - 8308764: Reporting errors from create_vm may crash

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14238/files
  - new: https://git.openjdk.org/jdk/pull/14238/files/6a58e430..b34adecd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14238&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14238&range=00-01

  Stats: 5839 lines in 236 files changed: 4327 ins; 858 del; 654 mod
  Patch: https://git.openjdk.org/jdk/pull/14238.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14238/head:pull/14238

PR: https://git.openjdk.org/jdk/pull/14238