Fix Issue 20763 - checkaction=context does not format pointers

[MoonlightSentinel]

This adds hexadecimal printing for pointers. Note that it still prefers toString for struct pointers if possible (because toString will probably be more useful than raw pointer values).

[dlang-bot]

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	20763	minor	checkaction=context does not format pointers

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 "master + druntime#3061"

[schveiguy]

Note that it still prefers toString for struct pointers if possible

This doesn't make sense. If you are using struct pointers, you are comparing two pointers, not the contents of the structs. It doesn't matter what the structs contain. The pointer values should be printed instead.

For instance:

struct S
{
   string val;
   string toString() { return "S(" ~ val ~ ")"; }
}

void main()
{
   auto s1 = S("hello");
   auto s2 = s1;
   assert(&s1 == &s2); // prints "Error: S(hello) != S(hello)" ?
}

[MoonlightSentinel]

RIght, that would be weird.
It'll always print the pointer now.