Drop lines in geom_sf() with missing linewidth

[teunbrand]

This PR aims to fix #5204.

Briefly, this PR just populates the non_missing_aes field of GeomPath, which is used in sf_grob() to determine what rows should be removed. Previously, missing linewidth would result in an error, now a warning. Also GeomPath$handle_na() now reads this field instead of hardcoding the aesthetics (because it seemed the right thing to do).

Reprex from #5204:

devtools::load_all("~/packages/ggplot2")
#> ℹ Loading ggplot2

pts <- sf::st_sf(
  geometry = sf::st_sfc(
    sf::st_linestring(matrix(0:3, nrow = 2)),
    sf::st_linestring(matrix(2:5, nrow = 2))
  ),
  linewidth = c(1, NA)
)

ggplot(pts) + geom_sf(aes(linewidth = linewidth))
#> Warning: Removed 1 row containing missing values or values outside the scale range
#> (`geom_sf()`).

^{Created on 2023-11-13 with reprex v2.0.2}

[thomasp85]

LGTM

[teunbrand]

Thanks for reviewing!