[r] Prepare for CRAN [long-term tracker]

[johnkerl]

Follow-on from #1567

• ​​Add/update CRAN comments (this is not an actual requirement at CRAN)
• ​​Submit to R-hub builder and verify no errors (prep for release to CRAN, not a GA blocker) (R-hub may fail due to our build process, is also challenged by our long list of dependencies, first attempt just failed for DE)
• Audit relative to the one authorative manual Writing R Extensions (with nicer rendering here)
• Audit relative to CRAN Repository Policy document
• Change build process to not require download at build time, need to vendor in capnp and spdlog, see CRAN Repository Policy 'External Libries' and 'Using Rust' along with (on email list) preference for 'vendored' over downloaded (this may be a "maybe" as a) use system libs first and b) can ask for forgiveness here)
• Pass R CMD check --as-cran on r-release as a minimal layer
• Pass R CMD check --as-cran on r-devel (in docker, locally [ I keep it on Ubuntu ], rhub, win-builder (inapplicable, no Windows package), mac-builder (works, has cnake and git)
• Pass R CMD check --use-valgrind (and inspect *.Rout files created) which currently errors and would lead to CRAN removal post-acceptance
• Pass all the "informal checks" the "new package submission desk" runs on eg authors, credits, references, ...
• Utilise experience of at least three contributors with active CRAN packages
• Update our release procedure to reflect publishing to CRAN
• Update the user-facing readme/docs to refer to CRAN instead of r-universe

[eddelbuettel]

In my experience the CRAN_comments.md is a myth. I have never heard anyone from CRAN recommending or requesting it yet I heard repeatedly that whatever was written in it was ignored. To be best of my understanding it serves primarily for pre-release notekeeping.

[eddelbuettel]

I took the liberty of co-assigning @aaronwolen and @mojaveazure who both have 'CRAN battle experience' too.

[johnkerl]

@eddelbuettel what steps remain to bring this issue to closure?

[eddelbuettel]

There was a bit of a sentiment recently that maybe CRAN release does not buy as all that that we don't already have with r-universe. Happy to chat off-line.

[johnkerl]

Per internal discussion we will revisit this once TileDB-R has been removed as a dependency from TileDB-SOMA-R. See also #2406.