Test ADM integrals with a boosted Schwarzschild solution.

[iago-mendes]

Proposed changes

This PR tests the ADM mass and ADM linear momentum calculations with a spacetime solution that has a conformal factor different than 1.

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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.

Further comments

[nilsvu]

You can squash. Best fix the clang-tidy issues while you're at it.