Add validation for RADMAX_2D MAGIC data

[registerrier]

With the addition of energy dependent ON region, this new spectral extraction technique must be validated. The two MAGIC Crab runs can be used to do that.

[morcuended]

The energy-dependent ON/OFF region technique is actually used in the LST-1 validation #152. I think this is enough to validate this. No need to create another test using MAGIC data.

[morcuended]

I think this can be closed as validated here https://github.com/gammapy/gammapy-benchmarks/tree/main/validation/lst1-dl3-crab