GH-39041:[R] Improve update-checksum.R output

[assignUser]

Rationale for this change

The script was to quiet.

What changes are included in this PR?

Fix regex and add some output:

Rscript tools/update-checksums.R 14.0.0                                                                           1 ✘
[1] "Extracting libarrow binary paths from tasks.yml"
[1] "Downloading windows/arrow-14.0.0.zip.sha512"
[1] "Converting windows/arrow-14.0.0.zip to windows style line endings"
[1] "Downloading linux-openssl-1.0/arrow-14.0.0.zip.sha512"
[1] "Downloading linux-openssl-1.1/arrow-14.0.0.zip.sha512"
[1] "Downloading linux-openssl-3.0/arrow-14.0.0.zip.sha512"
[1] "Downloading darwin-arm64-openssl-1.1/arrow-14.0.0.zip.sha512"
[1] "Downloading darwin-arm64-openssl-3.0/arrow-14.0.0.zip.sha512"
[1] "Downloading darwin-x86_64-openssl-1.1/arrow-14.0.0.zip.sha512"
[1] "Downloading darwin-x86_64-openssl-3.0/arrow-14.0.0.zip.sha512"
[1] "Checksums updated successfully!"

Are these changes tested?

locally

Are there any user-facing changes?

no

• Closes: [R] Improve UX of update-checksums.R #39041

[paleolimbot]

You're the only person who is likely to see this output so I trust that the output is useful to you! I do think you want cat() instead of print() though (which will get rid of the extraneous [1] prefixes in your output).

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 6 benchmarking runs that have been run so far on merge-commit 7346bdf.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 4 possible false positives for unstable benchmarks that are known to sometimes produce them.