Linear algebra/power iteration (#2190)

* Initial commit of power iteration.

* Added more documentation for power iteration and rayleigh quotient

* Type hinting for rayleigh quotient

* Changes after running black and flake8.

* Added doctests, added unit tests. Removed Rayleigh quotient as it is not needed.

* Update linear_algebra/src/power_iteration.py

Changed convergence check line.

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update linear_algebra/src/power_iteration.py

Named tests more clearly.

Co-authored-by: Christian Clauss <cclauss@me.com>

* Changed naming in test function to be more clear. Changed naming in doctests to match function call.

* Self running tests

Co-authored-by: Zeyad Zaky <zeyadzaky@Zeyads-MacBook-Pro.local>
Co-authored-by: Christian Clauss <cclauss@me.com>