For a plain struct with no field defaults and no constructor arguments,
the `A()` call path returned `zeroinitializer` directly instead of
constructing into the storage provided by `new`. Consequences for
`p: A* = new A()`:
- the malloc block was leaked,
- the struct value was materialized into an entry alloca by coercion,
so `p` pointed at the frame,
- the slife scope-exit free then freed a stack address (heap corruption / 0xC0000374).
Reuse the constructor path whenever a `new` storage descriptor is
pending, so `_translate_struct_ctor` zero-initializes the heap block and
returns its pointer.
Also guard the compiler-owned `new ... slife` binding: the target slot
must be a pointer variable, otherwise a value-typed `T` target would make
the scope-exit free load the struct value and bitcast it to a pointer.
Probe: `new heap A()`, `new A()`, `new stack A()` and `new heap hlife A()`
on a field-only class all print the expected values and exit 0; the
generated IR frees the malloc pointer instead of a stack slot.
Self-host 110/110; ListTest, GenericTest3, PtrOpProbe and HashLibTest
pass; NewTest, NewLifetimeTest, StructTest, EscapeOkTest and
OopInheritTest pass. NewAstTest and GenericOopTest fail the same way on
the previous compiler (pre-existing).
TermiNexus
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