add new constructor for TensorCI2 to initialize with local pivots list

[YoshihiroMichishita]

This PR updates src/tensorci2.jl to add a new constructor for TensorCI2 to inherit the local pivots of the previous search.
We also add the trivial testset to test/test_tensorci2.jl below:

@testset "inherit_local_pivots" begin
        Random.seed!(1234)

        N = 10
        M = rand(Float64, N, N)
        f(v) = M[v[1], v[2]] # 2D function
        localdims = fill(N, 2)
        mbd = 5

        tci, ranks, errors = TCI.crossinterpolate2(Float64, f, localdims; maxbonddim=mbd)
        tci2 = TCI.TensorCI2{Float64}(f, localdims, tci.Iset, tci.Jset)
        @test tci2.maxsamplevalue == tci.maxsamplevalue
    end

[shinaoka]

Thank you. We can check the consistency between tci.Iset and tci2.Iset (and the same for Jset).

[shinaoka]

Inherit Iset/Jset from the previous evaluation.

A better description may be "Initialize a TCI2 object with local pivot lists"?
This is because we do not necessarily inherit from a previous result.

[YoshihiroMichishita]

Thank you for your comments.
I updated the test and description.