RFR: 8259392: Zero error reporting is broken after JDK-8255711

[Aleksey Shipilev]

This manifests on the following `tier1` tests with Linux x86_64 Zero:

runtime/ErrorHandling/ErrorFileRedirectTest.java
runtime/ErrorHandling/SecondaryErrorTest.java
runtime/memory/ReadFromNoaccessArea.java
runtime/Unsafe/InternalErrorTest.java
runtime/Safepoint/TestAbortVMOnSafepointTimeout.java

00:17:25 #  Internal Error (/home/shade/trunks/jdk/src/hotspot/os_cpu/linux_zero/os_linux_zero.cpp:94), pid=739632, tid=739633
00:17:25 #  Error: ShouldNotCall()

address os::Posix::ucontext_get_pc(const ucontext_t* uc) {
  ShouldNotCallThis(); <---- crash here
  return NULL; // silence compile warnings
}

I believe the generification in JDK-8255711 applies to Zero awkwardly. 

Zero is awkward in the sense it is too generic for its own good. It does not have any access to crash context decoders, and that is why `ucontext_*` parsers are `ShouldNotCallThis()`-ed. Before JDK-8255711, Zero error reporting code was specially crafted to avoid this, apparently.

There are at least two problems:
 1. `ucontext_get_pc` in unimplemented, so we can special-case those for Zero. Instead of returning a bogus value from Zero implementation, I decided to just special-case at its critical use in error reporting.
 2. generic `VMError::report_and_die` circles back at Zero's unimplemented `os::fetch_frame_from_context`. Before JDK-8255711, Zero did `fatal()` that avoided this trouble. The patch ignores the context to match that behavior.

While the regression starts at JDK 16, it affects the path when VM is already crashing, so should not affect product quality per se. Therefore, I would prefer to get it to JDK 17 for some testing, and then maybe consider it for 16.0.{1,2}.

Also, this changeset kills the cat.

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Commit messages:
 - 8259392: Zero error reporting is broken after JDK-8255711

Changes: https://git.openjdk.java.net/jdk/pull/1980/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1980&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259392
  Stats: 19 lines in 1 file changed: 6 ins; 6 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1980.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1980/head:pull/1980

PR: https://git.openjdk.java.net/jdk/pull/1980