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ARROW-17252: [R] Intermittent valgrind failure (#13773)

This PR fixes intermittent leaks that occur after one of the changes from ARROW-16444: when we drain the `RecordBatchReader` that is emitted from the plan too quickly, it seems, some parts of the plan can leak (I don't know why this happens).

I tried removing various pieces of the `RunWithCapturedR()` changes (see #13746) but the only thing that removes the errors completely is draining the resulting `RecordBatchReader` from R (i.e., `reader$read_table()`) instead of in C++ (i.e., `reader->ToTable()`). Unfortunately, for user-defined functions to work in a plan we need a C++ level `reader->ToTable()`. I took the approach here of disabling the C++ level read by default, requiring a user to opt in to the version of `collect()` that works with a UDF. It's not ideal, but definitely safer (and more clearly marks the user-defined function behaviour as experimental).

I was able to replicate the original leaks but they are few and far between...our tests just happen to create and destroy many, many exec plans and something about the CI environment seems to trigger these more reliably (although the errors don't always occur there, either). Most of the leaks are small but there were some instances where an entire `Table` leaked.

Authored-by: Dewey Dunnington <dewey@fishandwhistle.net>
Signed-off-by: Neal Richardson <neal.p.richardson@gmail.com>