improved test for procrustes step and added third order expansion

[mkhona-nvidia]

Added the third order expansion and step size with line search from XL Li.

Improved test for procrustes_step after discussion with XL Li

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[mkhona-nvidia]

/ok to test 172c725

[mkhona-nvidia]

/ok to test 9859c48

[skyw]

Could you break it to two PRs, one for improving test, one for new functionality?
Review of test only change can be much lighter and faster.

[mkhona-nvidia]

/ok to test 6ef6f90

[mkhona-nvidia]

Could you break it to two PRs, one for improving test, one for new functionality? Review of test only change can be much lighter and faster.

it's a tiny change, and order=3 and order=2 should work interchangeably. all test are identical for order=2 and order=3 and the new test comparing them only tests convergence speed (less steps needed)

[mkhona-nvidia]

/ok to test e4e5d65

[skyw]

let me take a stab on the main order 2 and 3 function. If nothing better comes up, we can merge as it is.

A few small things need to be fixed also.

[mkhona-nvidia]

/ok to test 5f830fe