Add code to get common horizon coefs in ringdown distorted frame

[geoffrey4444]

Proposed changes

This PR is the first in a set that will enable transitioning from merger to ringdown in binary black hole simulations. This PR adds a C++ function that reads in common horizon coefficients from a file and transforms them to the ringdown distorted frame. A future PR will add a pybinding to this function and use that binding in an update to the Ringdown pipeline.

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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

[geoffrey4444]

I will fix the clang-tidy failures and look into why clang is happy but gcc isn't

[geoffrey4444]

Clang-tidy is fixed, and the gcc test failures are fixed. The test that did fail is unrelated to this PR

[knelli2]

In order to avoid reading all coefficients in, use get_data_subset instead.

  const Matrix ahc_times = ahc_h5_file.get<h5::Dat>(
          surface_subfile_name).get_data_subset({0}, 0, ahc_inertial_h5.size());

[geoffrey4444]

except I want the last requested_number_of_times_from_end , not the first requested_number_of_times_from_end

[knelli2]

If this is just supposed to be a Schwarzschild horizon of radius 1, you could do

const ylm::Strahlkorper<Frame::Grid> expected_strahlkorper{
    l_max, 1.0, {0.0, 0.0, 0.0};

[geoffrey4444]

I deliberately wanted it to be a Kerr horizon with spin 0.8, so some coefs are nontrivial

[knelli2]

Oh oops I misread this. The 8 blended in with all the 0s

[knelli2]

Looks good. Squash

[geoffrey4444]

Test failures look to me unrelated to this PR

[knelli2]

Yeah they do look unrelated, but I restarted them anyways. If there are still timeouts, I'll just merge this.