Local minimums in zeta search for primal hybrid

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Summary

In the primal hybrid estimator, the binary search for zeta is finding attacks which are not the best globally, and so overestimating security. Initially raised as a PR (#170)

To Reproduce

parameters = LWE.Parameters(n=2**17, q = 2**3104, Xs=ND.SparseTernary(p=96, m=96, n=2 ** 17), Xe=ND.DiscreteGaussian(3.19), m=oo)
LWE.primal_hybrid(parameters, babai=False, mitm=True)

>> rop: ≈2^152.3, red: ≈2^152.2, svp: ≈2^148.1, β: 248, η: 32, ζ: ≈2^15.0 ...

Expected behaviour

At least as good an attack without mitm switched on:

LWE.primal_hybrid(parameters, babai=False, mitm=False)
>> rop: ≈2^141.4, red: ≈2^141.3, svp: ≈2^136.1, β: 350, η: 2, ζ: ≈2^12.9 ...

and with a different minimum finder (ternary search), found

>> rop: ≈2^134.9, red: ≈2^134.6, svp: ≈2^132.2, β: 322, η: 33, ζ: ≈2^13.8 ...

Additional context

Believe this is happening for a lot of parameters which are large, based on replacing binary search with ternary search.