test_probs_pvt_fx: Test Probability function for private tests
In cmhoove14/LEMMAABMv4: COVID ABM

Function to generate probability of getting tested based on income, race, symptoms, and known contacts

test_probs_pvt_fx(
  income,
  race,
  essential,
  t_symptoms,
  state,
  t_since_contact,
  res_inf,
  res_type,
  tests_avail,
  symp_mult,
  race_mult,
  cont_mult,
  res_mult,
  nosymp_state_mult,
  symp_state_mult,
  hosp_mult
)

`income`	vector of agent income (1 = <50k ; 2 = 50-100k per year ; 3 = >100k per year)
`race`	vector of agent races
`essential`	binary of whether agent is an essential worker
`t_symptoms`	vector of time experiencing symptoms
`state`	infectious state
`t_since_contact`	vector of time left that person with known contact will consider contact a factor in testing decision
`res_inf`	Number of identified infectious individuals in residence
`res_type`	vector of residence types, "H", "N", "P"
`tests_avail`	number of tests available - creates multiplier to serve as proxy for how good identification of infected individuals is
`symp_mult`	multiplier for test probability for agents with symptoms. Acts on a per-day with symptoms basis, so 2 days with symptoms * 'symp_mult=10' would lead to 20x increase in test prob
`race_mult`	vector with same length as number of race groups with change in baseline probability of being tested
`cont_mult`	multiplier for test probability for agents with suspeceted contact
`res_mult`	multiplier for test probability for agents with known infection in their residence
`nosymp_state_mult`	multiplier for test probability for agents who are infected but not shopwing symptoms (Ia or Ip)
`symp_state_mult`	multiplier for test probability for agents who are infected andshowing symptoms (Im or Imh)
`hosp_mult`	multiplier for test probability for agents who are infected and hospitalized