Change the X Axis (Rotor Speed) in Campbell Diagram

[ViniciusTxc3]

Now, it's possible change the x axis (rotor speed) with variable speed_units in plot().

import ross as rs
import numpy as np

Q_ = rs.Q_
rotor = rs.rotor_example()
speed = np.linspace(0, 400, 101)
camp = rotor.run_campbell(speed)
fig = camp.plot(
        harmonics=[1, 2],
        damping_parameter="damping_ratio",
        frequency_range=Q_((2000, 10000), "RPM"),
        damping_range=(-0.1, 100),
        frequency_units="Hz",
        speed_units="RPM",
        )

This PR resolve, issue #1087.

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.52%. Comparing base (56f00c1) to head (d743b50).
Report is 4 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1105      +/-   ##
==========================================
- Coverage   84.56%   84.52%   -0.05%     
==========================================
  Files          35       34       -1     
  Lines        7990     7972      -18     
==========================================
- Hits         6757     6738      -19     
- Misses       1233     1234       +1     

Files with missing lines	Coverage Δ
ross/results.py	84.11% <ø> (-0.08%)	⬇️

... and 2 files with indirect coverage changes

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