[SAoC 2023] Replace DRuntime Hooks with Templates Weekly Update #9

[Teodor Dutu]

Hi,

This week I finished working on converting 
`_d_newarray{mTX,miTX,OpT}` to a single template and got the 
[PR](https://github.com/dlang/dmd/pull/15819) merged. They 
allocate and initialise multi-dimensional arrays. Similarly to 
[`_d_newarray{U,T,iT}`](https://github.com/dlang/dmd/pull/15299), 
`_d_newaraym*` are now implemented by a single hook: 
`_d_newarraymTX`. Previously the two hooks were used to 
differentiate between default-initialised and zero-initialised 
types. `_d_newarrayOpT` was the common implementation called by 
both `_d_newarraym{i,}TX` hooks. `_d_newarrayOpT` received an 
alias template argument: either `_d_newarrayiT` or `_d_newarrayT` 
which it used to allocate the innermost 1-D array.

Now `_d_newarraymTX` can be made much simpler: it simply calls 
`_d_newarrayT`, which in turn uses DBI to figure out how to 
initialise the array. In the following weeks I'll start working 
on `_d_arrayliteralTX` and `_d_assocarrayliteralTX`.

Thanks,
Teo