Merge roofline modules

[coleramos425]

At the moment, there are two areas where Omniperf computes Empirical Roofline data

1. src/utils/plot_roofline.py
2. src/omniperf_analyze/utils/roofline_calc.py

A lot of this code is duplicated so I propose we reorganize this into one module.

(1) is used in the standalone roofline capability (i.e. --roof-only) and generates a .pdf file with roofline leveraging matplotlib tools.
(2) returns critical data points for roofline to our Dash interface where a plot is sent to the html webpage