GH-46825: [R] Use smallest_decimal() from C++ instead of working out which decimal type to instantiate in R

[thisisnic]

Rationale for this change

R code duplicated code from C++

What changes are included in this PR?

Remove duplication

Are these changes tested?

There were existing tests

Are there any user-facing changes?

Nah

• GitHub Issue: [R] Use smallest_decimal() from C++ instead of working out which decimal type to instantiate in R #46825

[github-actions]

⚠️ GitHub issue #46825 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #46825 has no components, please add labels for components.

[jonkeane]

@github-actions crossbow submit -g r

[jonkeane]

This is great, I've triggered a larger run in case there's something off in weird places, but if that passes (or is no worse than main) this is a lovely simplification.

[github-actions]

Revision: b003303

Submitted crossbow builds: ursacomputing/crossbow @ actions-753b64161f

Task	Status
r-binary-packages
r-recheck-most
test-r-arrow-backwards-compatibility
test-r-depsource-bundled
test-r-depsource-system
test-r-dev-duckdb
test-r-devdocs
test-r-extra-packages
test-r-gcc-11
test-r-gcc-12
test-r-install-local
test-r-install-local-minsizerel
test-r-linux-as-cran
test-r-linux-rchk
test-r-linux-sanitizers
test-r-linux-valgrind
test-r-m1-san
test-r-macos-as-cran
test-r-minimal-build
test-r-offline-maximal
test-r-offline-minimal
test-r-rhub-debian-gcc-devel-lto-latest
test-r-rhub-ubuntu-gcc12-custom-ccache
test-r-rhub-ubuntu-release-latest
test-r-rocker-r-ver-latest
test-r-rstudio-r-base-4.1-focal
test-r-rstudio-r-base-4.2-focal
test-r-ubuntu-22.04
test-r-versions

[thisisnic]

• test-r-extra-packages is failing because there aren't any relevant nightlies
• test-r-minimal-build complains about xsimd when building Arrow [1]. Unsure if the function needs it or it's a fluke? I'll retrigger
• test-r-rocker-r-ver-latest appeared to time out

[1]

In file included from /arrow/cpp/src/arrow/util/bpacking_simd_default.cc:19:
/arrow/cpp/src/arrow/util/bpacking_simd128_generated_internal.h:27:10: fatal error: xsimd/xsimd.hpp: No such file or directory
   27 | #include <xsimd/xsimd.hpp>
      |          ^~~~~~~~~~~~~~~~~
compilation terminated.
make[2]: *** [src/arrow/CMakeFiles/arrow_util.dir/build.make:244: src/arrow/CMakeFiles/arrow_util.dir/util/bpacking_simd_default.cc.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:830: src/arrow/CMakeFiles/arrow_util.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
[ 26%] Building CXX object src/arrow/CMakeFiles/arrow_array.dir/array/data.cc.o

[thisisnic]

@github-actions crossbow submit test-r-minimal-build

[github-actions]

Revision: b003303

Submitted crossbow builds: ursacomputing/crossbow @ actions-c9bb5ed09b

Task	Status
test-r-minimal-build

[thisisnic]

@github-actions crossbow submit -g r

[github-actions]

Revision: daa3173

Submitted crossbow builds: ursacomputing/crossbow @ actions-23f039f54f

Task	Status
r-binary-packages
r-recheck-most
test-r-arrow-backwards-compatibility
test-r-depsource-bundled
test-r-depsource-system
test-r-dev-duckdb
test-r-devdocs
test-r-extra-packages
test-r-gcc-11
test-r-gcc-12
test-r-install-local
test-r-install-local-minsizerel
test-r-linux-as-cran
test-r-linux-rchk
test-r-linux-sanitizers
test-r-linux-valgrind
test-r-m1-san
test-r-macos-as-cran
test-r-minimal-build
test-r-offline-maximal
test-r-offline-minimal
test-r-rhub-debian-gcc-devel-lto-latest
test-r-rhub-ubuntu-gcc12-custom-ccache
test-r-rhub-ubuntu-release-latest
test-r-rocker-r-ver-latest
test-r-rstudio-r-base-4.1-focal
test-r-rstudio-r-base-4.2-focal
test-r-ubuntu-22.04
test-r-versions

[thisisnic]

OK, this looks good, merging!