Option to `eval_select()` to disallow empty selections

[DavisVaughan]

i.e.

library(tidyselect)
library(rlang)

df <- data.frame(x = 1)

# In some cases, I'd like this to be an error
eval_select(expr(starts_with("foo")), df)
#> named integer(0)

In tidyr, we have 3 places where we check that the result of eval_select() selects "at least 1 column", like
https://github.com/tidyverse/tidyr/pull/1241/files#diff-082bcbb672e069ebb562fb3b877b4d9457f867d89ba382224e1041ce90a89ff4R308

I like that this is already an error by default:

library(tidyselect)
library(rlang)

df <- data.frame(x = 1)

eval_select(expr(y), df)
#> Error: Can't subset columns that don't exist.
#> x Column `y` doesn't exist.

but I think it might make sense to have an ultra strict mode as well that can't ever result in an empty selection