Nest survival/hazard predictions for scalar eval_time for flexsurv engines

[hfrick]

Before:

library(censored)
#> Loading required package: parsnip
#> Loading required package: survival

survival_reg(engine = "flexsurv") %>%
  fit(Surv(time, status) ~ age + sex, data = lung) %>%
  predict(lung[1:3, ], type = "survival", time = 100) 
#> [snip: parsnip warning on `time` arg]
#> # A tibble: 3 × 2
#>   .time .pred_survival
#>   <dbl>          <dbl>
#> 1   100          0.803
#> 2   100          0.820
#> 3   100          0.849

^{Created on 2023-04-11 with reprex v2.0.2}

After:

library(censored)
#> Loading required package: parsnip
#> Loading required package: survival

survival_reg(engine = "flexsurv") %>%
  fit(Surv(time, status) ~ age + sex, data = lung) %>%
  predict(lung[1:3, ], type = "survival", eval_time = 100) 
#> # A tibble: 3 × 1
#>   .pred           
#>   <list>          
#> 1 <tibble [1 × 2]>
#> 2 <tibble [1 × 2]>
#> 3 <tibble [1 × 2]>

^{Created on 2023-04-11 with reprex v2.0.2}

[github-actions]

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