Review emit interpolation
As mentioned in https://github.com/nim-lang/Nim/issues/12036#issuecomment-524890898
emit interpolation does not use backtick, unlike quote do and template identifier injection.

A thorough review of emit interpolation should be done to avoid future breakage.

https://github.com/mratsim/Arraymancer/blob/77c11a0d9931a48c20ca5f070b2c933a5fbdcd5f/src/linear_algebra/helpers/triangular.nim#L27-L49