[R] Sub-day precision Date class must be converted to integers by floor, not ceil

[eitsupi]

Describe the bug, including details regarding any error messages, version, and platform.

Same as apache/arrow-nanoarrow#665

d <- as.Date(-0.1)
d
#> [1] "1969-12-31"
as.vector(arrow::as_arrow_array(d))
#> [1] "1970-01-01"

^{Created on 2024-10-22 with reprex v2.1.1}

Component(s)

R