RFR: 8253433: Remove -XX:+Debugging product option

[Coleen Phillimore]

On Thu, 1 Oct 2020 01:30:16 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> The Debugging option shouldn't be used on the command line.  There's a SuppressErrorAt option to ignore certain
>> asserts, if there is some situation needing that. Debugging should never be used.
>> Tested with tier1 tests on 4 platforms.
>
> Seems fine. Thanks.

>This is really just about the one existing assignment.
See the Command context class in debug.cpp. This variable probably shouldn?t be set/reset
much of anywhere else.

There's also a place in macroAssembler that sets it to true also, that calls os::print_location() where we also want to
prevent crashes.  We could rewrite that to use the debug.cpp find functions but doesn't seem worth doing.

Thank you for the code reviews.

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PR: https://git.openjdk.java.net/jdk/pull/434