std.typecons: Greatly simplify scoped()

[kinke]

The previous implementation was just terrible, presumably dating back to when align(N) was buggy.

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[kinke]

FYI @ljmf00.

[ljmf00]

Ahhhhhgg, we are having the same problem as the TLS alignment on druntime.

[kinke]

Yeah, looks like there's a corresponding DMD backend issue for 32-bit COFF too. :(

[kinke]

Blocked by https://issues.dlang.org/show_bug.cgi?id=16098.

[PetarKirov]

@kinke Windows CI tests are failing:

object.Error@(0): Access Violation
----------------
0x02A3E8ED in rt_finalize2
0x019AF400 in object.destroy!(false, std.typecons.__unittest_L8826_C9.C1long).destroy at D:\a\1\dmd\druntime\import\object.d(4154)
0x019C8577 in std.typecons.__unittest_L8826_C9.alignmentTest at D:\a\1\phobos\std\typecons.d(8856)
0x019C8526 in std.typecons.__unittest_L8826_C9 at D:\a\1\phobos\std\typecons.d(8874)
0x02A4FCB3 in int object.ModuleInfo.opApply(scope int delegate(object.ModuleInfo*)).__lambda2(immutable(object.ModuleInfo*))
0x02A4D0A6 in _d_run_main2
0x02A37234 in _d_run_main
0x00FBEECC in unittest._d_cmain!().main at D:\a\1\dmd\druntime\import\core\internal\entrypoint.d(30)
0x771105C9 in BaseThreadInitThunk
0x776E784D in RtlGetAppContainerNamedObjectPath
0x776E781D in RtlGetAppContainerNamedObjectPath
1/133 modules FAILED unittests

[kinke]

Yeah, same issue as ~a year ago. I assumed the compiler fix for https://issues.dlang.org/show_bug.cgi?id=16098 finally fixed this for DMD, but no it didn't.