[R] Make expect_dplyr_equal() a bit stricter

[asfimport]

Add a warning_msg = NA or the like as an argument to expect_dplyr_equal() that check + ensures we aren't pulling data into R and then running the dplyr query.

But will need to re-arrange where warnings like

arrow/r/tests/testthat/test-dplyr-mutate.R

Line 198 in 7692461

"Expression across.*not supported in Arrow"

are being expected.

Reporter: Jonathan Keane / @jonkeane
Assignee: Neal Richardson / @nealrichardson

_{Note: This issue was originally created as ARROW-12092. Please see the migration documentation for further details.}

[asfimport]

Neal Richardson / @nealrichardson:
I did this in ARROW-12994

[asfimport]

Todd Farmer / @toddfarmer:
Transitioning issue from Resolved to Closed to based on resolution field value.