Add KleinGordonWorldtubeData and its option tag

[Sizheng-Ma]

Proposed changes

This PR adds an abstract base class KleinGordonWorldtubeData that handles analytic worldtube data for Klein-Gordon Cce. The future Cce executable built upon it aims to provide a battery of tests for the system, e.g., bouncing Schwarzschild black hole in Sec. V of Moxon et al.

The content of KleinGordonWorldtubeData is fully in parallel with WorldtubeData

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Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

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