refactor(r): Refactor ArrowArray(Stream) -> R Vector conversion

[paleolimbot]

The initial version of converting ArrowArray (or stream of them) to R is implemented in C and is difficult to understand. Not only is this difficult because of the verbose C, the dispatch portion is implemented almost completely twice (once for a single array, once for an array stream). It is at a point currently where it is difficult for me, let alone an external contributor, to add features or fix bugs. Time to refactor!

This approach uses C++ classes/virtual method dispatch to handle the different types of vector conversions. This is similar to how the arrow R package does this except the Arrow R package uses the Arrow C++ converter infrastructure/heavy templating to do dispatch. Here we use a switch() and eat the per-batch and per-column virtual method call.

Work in progress!

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 35.44474% with 479 lines in your changes are missing coverage. Please review.

Project coverage is 86.09%. Comparing base (c7a1236) to head (2afc7b8).

Files	Patch %	Lines
r/src/vctr_builder_int.h	2.98%	65 Missing :warning:
r/src/vctr_builder_int64.h	0.00%	59 Missing :warning:
r/src/vctr_builder_dbl.h	10.52%	51 Missing :warning:
r/src/vctr_builder.cc	73.21%	45 Missing :warning:
r/src/vctr_builder_difftime.h	37.50%	40 Missing :warning:
r/src/vctr_builder_other.h	11.11%	40 Missing :warning:
r/src/vctr_builder_base.h	30.35%	39 Missing :warning:
r/src/vctr_builder_lgl.h	5.26%	36 Missing :warning:
r/src/vctr_builder_chr.h	5.88%	32 Missing :warning:
r/src/vctr_builder_blob.h	4.00%	24 Missing :warning:
... and 5 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #392 +/- ## ========================================== - Coverage 88.74% 86.09% -2.66% ========================================== Files 81 97 +16 Lines 14398 15091 +693 ========================================== + Hits 12778 12993 +215 - Misses 1620 2098 +478 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.