Adding detector class for calculating LISA projections and response function

[acorreia61201]

No description provided.

[ahnitz]

We should mimic the interface here used for the ground based detectors e.g. try to make them as similar as possible. Also, we want to be a little bit future proof as we'll likely have more than just the faslisa implementation and so will want to be able to switch between approximations / implementations of the response.

[acorreia61201]

The LISA_detector class in my most recent commit should be sufficient for calculating LISA TDI channels from radiation frame PyCBC waveforms. I am able to replicate the results from the FastLISAResponse tutorial (shown here), with additional functionality for inputting reference times. By default, the TDI channels are calculated using lisatools.detector.ESAOrbits (a simulated realistic orbital file), but orbital information can be input using the Orbits base class in LISA Analysis Tools. All modifications use the most recent versions of FastLISAResponse (ver. 1.0.5) and LISA Analysis Tools.

One pending issue regards the usage of Orbits.configure, which will throw an error with the most recent version of LISA Analysis Tools. I have submitted a pull request to that repository that should solve the issue, but I am still awaiting a response from their development team. Additionally, I haven't been able to conduct timing tests on GPUs, as the most recent version of FastLISAResponse cannot be built with GPU support.

[ahnitz]

@acorreia61201 You'll want to rebase this PR, get the unittest to pass with your PR, and then demonstrate how this compares to say calling BBHx directly. E.g. can you post an example that reproduces BBHx output but using this class and say starting from IMRPhenomD?

[WuShichao]

@acorreia61201 Can you do this test: from the typical parameter space (prior) of SMBHB and stellar-mass BBH to compute the overlap between BBHx plugin and this PR? Let's do 1000 draw and plot histogram of overlap (not the match).