[R] Rename na.min_count to min_count and na.rm to skip_nulls

[asfimport]

In ARROW-13501 and ARROW-13620, the options passed to make_compute_options are named na.min_count and na.rm. For consistency with other options, they should be named min_count and skip_nulls to match the C++ function options.

Reporter: Ian Cook / @ianmcook
Assignee: Neal Richardson / @nealrichardson

Related issues:

• [R] Bindings for count aggregation (relates to)
• [R] Binding for n_distinct() (relates to)

PRs and other links:

• GitHub Pull Request #11079

_{Note: This issue was originally created as ARROW-13820. Please see the migration documentation for further details.}

[asfimport]

Neal Richardson / @nealrichardson:
Issue resolved by pull request 11079
#11079