Fix #10785 - Fix invalid access of GC memory from destructor when inside a GC finalizer with debug build

[schveiguy]

This caused a segfault in testing the new GC on windows, as this new GC is more aggressive uncomitting freed memory.

redo of #10786

[dlang-bot]

Thanks for your pull request, @schveiguy!

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Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "stable + phobos#10787"

[kinke]

Style checker:

std/uni/package.d(1788:20)[warn]: Local imports should specify the symbols being imported to avoid hiding local symbols.

[schveiguy]

stylechecker fixed

[Geod24]

Style checker:

We really need to get rid of this error message. It's been 20 or 30 releases that this bug has been fixed IIRC.

[schveiguy]

Need another PR, there is still some CowArray problems with the reference count...