Fix Trotter unit tests

[TysonRayJones]

The current Trotter function unit tests call REQUIRE inside loops with $2^{16}$ iterations, inflating the assertion count. As a result, a serial-deployment "applyTrotterizedImaginaryTimeEvolution" test results in (262153 assertions in 1 test case).

Relatedly, they appear to be comparing two Quregs per-amplitude, via

// iterating over i
qcomp other_amp = getQuregAmp(qureg, i);
qreal other_mag = other_amp.real() * other_amp.real() +  other_amp.imag() * other_amp.imag();

(instead of simply calcProbOfBasisState), but it is unclear why the Qureg must be compared via magnitude instead of the existing Qureg-wide amplitude comparisons. Fix this!

[otbrown]

Whoops 😅 apologies, very much a product of a something-better-than-nothing before the project ended approach I'm afraid

[TysonRayJones]

Hehe no problem at all - indeed perfect is the enemy of complete!