Armijo linesearch does not allocate the right candidate point type

[kellertuer]

If you try to run a code on typed points like

using Manopt, Manifolds
using ManifoldDiff: grad_distance
M = Hyperbolic(2)
data = PoincareBallPoint.([ [0.1, 0.2], [0.3,0.25], [0.35,0.4] ])
n = length(data)
f(M, p) = sum(1 / (2 * n) * distance.(Ref(M), Ref(p), data) .^ 2)
grad_f(M, p) = sum(1 / n * grad_distance.(Ref(M), data, Ref(p)));
m1 = gradient_descent(M, f, grad_f, data[1])

This errors since the candidate point within Armijo line search is an array (from the default representation on Hyperbolic) due to this line

Manopt.jl/src/plans/stepsize/stepsize.jl

Line 106 in 962ae49

candidate_point::P = allocate_result(M, rand),

allocating a default random point. A solution could be to pass the initial point to step sizes as well (optionally, so they rand otherwise to be nonbreaking) and use that points type to allocate the candidate.

Might affect other step sizes as well that are linesearch based (i.e. need a candidate).