Duplication of DEBUG configuration

Duplication of DEBUG configuration

`DEBUG` variable is in files:
- `numba_dppy/dpnp_glue/__init__.py`
- `numba_dppy/compiler.py`
- `numba/core/config.py`

It should be in files:
- `numba_dppy/config.py`
- `numba/core/config.py`

numba-dppy `DEBUG` should be set as numba `DEBUG` by default.
It should be able to set via `NUMBA_DPPY_DEBUG` env variable.