update sdp and polynomial interface

[lucaferranti]

This PR updates SDP and the polynomial interface

• There was some boilerplate code in SDP, no need to differentiate between 1D and higher dimension, also no need to allocate the vector Bi, a generator can be used
• Now _enclose(SumOfSquaresEnclosure) expects as a second input a polynomial instead of a function, this makes sense, because SOS works only for polynomials and the previous implementation was converting the function to polynomial. This change allows to avoid using the @polyvar macro, which is polynomial backend specific, this way we can only use the interface package MultivariatePolynomials.jl as dependency.
• removed DynamicPolynomials.jl as dependecy as replaced with MultivariatePolynomials.jl which is now optional (fixes replace DynamicPolynomials.jl by MultivariatePolynomials.jl #68)

[schillic]

Looks good, but I have one question.