refactor: refactor the plot widget class

[weibullguy]

Does this PR introduce a breaking change?

• Yes
• No

Describe the purpose of this pull request.

To refactor the plot widget.

Describe how this was implemented.

Made one code smell fix. This class must have been refactored some time in the past.

Describe any particular area(s) reviewers should focus on.

None

Provide any other pertinent information.

Closes #808

Pull Request Checklist

• Code Style

  • [ X] Code is following code style guidelines.

• Static Checks

  • Failing static checks are only applicable to code outside the scope of
    this PR.

• Tests

  • At least one test for all newly created functions/methods?

• Chores

  • Issue(s) have been raised for problem areas outside the scope of
    this PR. These problem areas have been decorated with an ISSUE: # comment.

[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
8.0% Duplication

[codecov]

Codecov Report

Merging #1040 (0c6a94e) into master (2e8689e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1040   +/-   ##
=======================================
  Coverage   95.20%   95.20%           
=======================================
  Files         144      144           
  Lines        5400     5400           
  Branches      574      574           
=======================================
  Hits         5141     5141           
  Misses        230      230           
  Partials       29       29           

Flag	Coverage Δ
3.6	95.20% <ø> (ø)
3.7	95.20% <ø> (ø)
3.8	95.20% <ø> (ø)

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