dmd.template-_d_newarratmT.dd

`_d_newarray{mTX,miTX,OpT}` are converted to a single template: `_d_newarraymTX`

The template `_d_newarraymTX` now uses DBI to check what type of initialiser is required by the type of the elements in the array.
Thus it replaces both `_d_newarraymTX` and `_d_newarraymiTX`.

`_d_newarrayOpT` was the generic implementation of both of the above hooks.
It first allocated the "outer" arrays as pointer arrays and then it called either `_d_newarrayT` or `_d_newarrayiT`, to allocate initialise the "inner" 1-dimensional arrays accordingly.
Now this is no longer needed due to the merge between `_d_newarraymTX` and `_d_newarraymiTX`.

Now the compiler performs the following lowering:

---
S[][] s = new S[][](2, 3)

// is now lowered to:
S[] s = _d_newarraymTX!(S[][], S)([2, 3]);
---

This change adds the new template to `core.internal.array.construction`.