Deprecate `.data` in data-expressions

[lionel-]

To make programming with data-masking and programming with selections completely distinct.

[lionel-]

Do we need an all_of() variant that expects exactly 1 variable?

[dblodgett-usgs]

Out of curiosity, was the fact that this pattern has been recommended in this vignette https://dplyr.tidyverse.org/articles/programming.html for quite some time taken into account when this change was made? It seems like it's causing a lot of people to go changing a lot of code ... is it really needed?