decompose get_nse_state into two separate functions

[zhichen3]

Here I separated get_nse_state into two separate functions, one that calculates the exponent part of the nse mass fraction (depends on chemical potentials) and the other calculates components that do not depend on chemical potentials.

This way we don't have to compute unnecessary parts when we solve for chemical potentials, mu_p and mu_n during hybrid solver, which includes getting the partition function.

Heres the new profile, it brings down # of calls for get_partition_functions from 900,000,000+ (from pr1274) to 200,000,000+

Flat profile:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total           
 time   seconds   seconds    calls   s/call   s/call  name    
 18.17     11.93    11.93 17968009     0.00     0.00  void fcn<burn_t>(amrex::Array1D<double, 1, 2>&, amrex::Array1D<double, 1, 2>&, burn_t const&, int&) [clone .constprop.0]
 12.44     20.10     8.17    58352     0.00     0.00  Castro::valid_zones_to_burn(amrex::MultiFab&)
  8.03     25.37     5.27 53037636     0.00     0.00  void apply_electrons<burn_t>(burn_t&)
  7.02     29.98     4.61  5332400     0.00     0.00  in_nse(burn_t&, bool)
  6.06     33.96     3.98 258295193     0.00     0.00  std::_Function_handler<amrex::GpuTuple<amrex::ValLocPair<double, amrex::IntVect> > (), amrex::ReduceData<amrex::ValLocPair<double, amrex::IntVect> >::ReduceData<amrex::ReduceOpMin>(amrex::ReduceOps<amrex::ReduceOpMin>&)::{lambda()#1}>::_M_manager(std::_Any_data&, std::_Any_data const&, std::_Manager_operation)
  6.00     37.90     3.94 190665624     0.00     0.00  std::_Function_handler<amrex::GpuTuple<int, int> (), amrex::ReduceData<int, int>::ReduceData<amrex::ReduceOpMax, amrex::ReduceOpMax>(amrex::ReduceOps<amrex::ReduceOpMax, amrex::ReduceOpMax>&)::{lambda()#1}>::_M_manager(std::_Any_data&, std::_Any_data const&, std::_Manager_operation)
  5.50     41.51     3.61  5249180     0.00     0.00  void nse_hybrid_solver<burn_t>(burn_t&, double)
  5.44     45.08     3.57  5381927     0.00     0.00  amrex::Vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::~Vector()
  4.28     47.89     2.81 13877485     0.00     0.00  void actual_eos<eos_input_t, burn_t>(eos_input_t, burn_t&)
  3.24     50.02     2.13  5257685     0.00     0.00  void hybrj<2, burn_t>(hybrj_t<2>&, burn_t const&)
  2.85     51.89     1.87  8988526     0.00     0.00  sneut5(double, double, double, double, double&, double&, double&, double&, double&)
  2.07     53.25     1.36  8609836     0.00     0.00  void fill_reaclib_rates<0, rate_t>(tf_t const&, rate_t&)
  2.03     54.58     1.33  8609836     0.00     0.00  void evaluate_rates<0, rate_t>(burn_t const&, rate_t&)
  1.55     55.60     1.02 56453976     0.00     0.00  fill_merge_indices(amrex::Array1D<int, 1, 2>&, double&, int, amrex::Array1D<double, 1, 22> const&, burn_t const&, amrex::Array1D<double, 1, 93> const&, amrex::Array1D<int, 1, 22> const&, double const&)
  1.53     56.61     1.01 236019664     0.00     0.00  get_partition_function(int, tf_t const&, double&, double&)
  1.29     57.46     0.85  8988526     0.00     0.00  rhs_nuc(burn_t const&, amrex::Array1D<double, 1, 23>&, amrex::Array1D<double, 1, 22> const&, amrex::Array1D<double, 1, 93> const&)
  0.87     58.03     0.57  8609836     0.00     0.00  void rate_ne20_to_he4_o16_derived<0>(tf_t const&, double&, double&)
  0.75     58.52     0.49  8609836     0.00     0.00  void rate_he4_ne20_to_p_na23_derived<0>(tf_t const&, double&, double&)
  0.73     59.00     0.48  8609836     0.00     0.00  void rate_si28_to_p_al27_derived<0>(tf_t const&, double&, double&)
  0.69     59.45     0.45  8609836     0.00     0.00  void rate_mg24_to_he4_ne20_derived<0>(tf_t const&, double&, double&)
  0.69     59.90     0.45  8609836     0.00     0.00  void rate_ar36_to_p_cl35_derived_removed<0>(tf_t const&, double&, double&)

[zingale]

this has conflicts now