RFR: 8338883: Add core dump info to -Xlog:os=info [v6]

[Gerard Ziemski]

> We add a small feature, which adds core dump info, which till now was only printed as part of hs_err log file, directly to stdout, when desired using log mechanism, i.e. `-Xlog:os=info`
> 
> For example, if we see:
> 
> `core dump info: core.28283`
> 
> we know all is set up correctly and we can expect a core file if java process crashes. If we see:
> 
> `core dump info: Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again`
> 
> instead, however, we know that "ulimit -c unlimited" needs to be set.
> 
> Testing: 
> - passes `"MACH5 runtime/ErrorHandling/CreateCoredumpOnCrash.java"`
> - full MACH5 test in progress...

Gerard Ziemski has updated the pull request incrementally with one additional commit since the last revision:

  use warning to show when core dump is not going to happen

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/20734/files
  - new: https://git.openjdk.org/jdk/pull/20734/files/2c16cfbb..aa351e16

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20734&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20734&range=04-05

  Stats: 82 lines in 5 files changed: 42 ins; 16 del; 24 mod
  Patch: https://git.openjdk.org/jdk/pull/20734.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20734/head:pull/20734

PR: https://git.openjdk.org/jdk/pull/20734