Maintenance Release, PFN integration, VBLL surrogates, Classifier-based constraint support

Highlights

• Prior Fitted Network (PFN) surrogate model integration (#2784).
• Variational Bayesian last-layer models as surrogate Models (#2754).
• Probabilities of feasibility for classifier-based constraints in acquisition functions (#2776).

New Features

• Helper for evaluating feasibility of candidate points (#2733).
  • Check for feasibility in gen_candidates_scipy and error out for infeasible candidates (#2737).
  • Return a feasible candidate if there is one and return_best_only=True (#2778).
• Allow for observation noise without provided evaluation_mask mask in ModelListGP (#2735).
• Implement incremental qLogNEI via incremental argument to qLogNoisyExpectedImprovement (#2760).
• Add utility for computing AIC/BIC/MLL from a model (#2785).
• New test functions:
  • Multi-fidelity test functions with discrete fidelities (#2796).
  • Keane bump function (#2802).
  • Mixed Ackley test function (#2830).
  • LABS test function (#2832).
• Add parameter types to test functions to support problems defined in mixed / discrete spaces (#2809).
  • Add input validation to test functions (#2829).
• Add [q]LogProbabilityOfFeasibility acquisition functions (#2815).

Bug Fixes

• Remove hard-coded dtype from best_f buffers (#2725).
• Fix dtype/nan issue in StratifiedStandardize (#2757).
• Properly handle observed noise in AdditiveMapSaasSingleTaskGP with outcome transforms (#2763).
• Do not count STOPPED (due to specified budget) as a model fitting failure (#2767).
• Ensure that initialize_q_batch always includes the maximum value when called in batch mode (#2773).
• Fix posterior with observation noise in batched MTGP models (#2782).
• Detach tensor in gen_candidates_scipy to avoid test failure due to new warning (#2797).
• Fix batch computation in Pivoted Cholesky (#2823).

Other Changes

• Add optimal values for synthetic contrained optimization problems (#2730).
  • Update max_hv and reference point for Penicillin problem (#2771).
  • Add optimal value to SpeedReducer problem (#2799).
• Update nonlinear_constraint_is_feasible to return a boolean tensor (#2731).
• Restructure sampling methods for info-theoretic acquisition functions (#2753).
• Prune baseline points in qLogNEI by default (#2762).
• Misc updates to MES-based acqusition functions (#2769).
• Pass option to reset submodules in train method for fully Bayesian models (#2783).
• Put outcome transforms into train mode in model constructors (#2817).
• LogEI: select cache_root based on model support (#2820).
• Remove Ax dependency from BoTorch tutorials and reference Ax tutorials instead (#2839).

Deprecations and removals

• Remove deprecated gp_sampling module (#2768).
• Remove qMultiObjectiveMaxValueEntropy acquisition function (#2800).
• Remove model converters (#2801).