[Tests & Bug]: Power operator

At a previous merge request, the power operator was implemented over the classes of DccName and DccQuantityType.

However, that branch did not create any test case nor full review was done, thus the bug of the power operator does not always work. E.g.: When the data of the DccQuantityType is SiRealList the power operator fails.

In the scope of this ticket the following should be applied:

• Fix the behavior of the power operator.
• Integrate test cases for DccQuantityType and its math.

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UPDATE

For the power operator, only adimensional values are allowed. These values are defined by a DsiUnit with:

• Value r"\one"
• Value where all the units are equal and nullify each other. E.g.: r"\volt\per\volt"
• Value where all units nullify each other in base units. E.g.: `"r"\joule\per\kilogram\metre\tothe{2}\second\tothe{-2}""