GH-32123: [R] Expose azure blob filesystem

[marberts]

Rationale for this change

This PR adds support for Azure. The Arrow R package already has support for AWS and GCS, and the Arrow C++ library has had support for Azure for a couple years now. Support for Azure is already available in pyarrow.

This would close #32123.

What changes are included in this PR?

• A new class AzureFileSystem that's analogous to S3FileSystem/GcsFileSystem, along with a helper function az_container() that's analogous to s3_bucket()/gcs_bucket().

• Updates to src/filesystem.cpp to interact with the machinery in arrow/filesystem/azurefs.h.

• Updates to the configuration and build scripts to support building with support for Azure.

• Updates to the vignettes on cloud storage, installation, and developer setup.

Are these changes tested?

Yes. See tests/testthat/test-azure.R.

Are there any user-facing changes?

Yes. There is a new function az_container(), serving the analogous role to s3_bucket()/gcs_bucket(), along with an R6 class AzureFileSystem, again serving the same role as S3FileSystem and GcsFileSystem. There is also a function arrow_with_azure() to indicate if Arrow was built with support for Azure.

• GitHub Issue: [R] Expose Azure Blob Storage filesystem #32123

[github-actions]

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See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[github-actions]

⚠️ GitHub issue #32123 has been automatically assigned in GitHub to PR creator.

[marberts]

The CI is failing because the Azure C++ SDK depends on libxml2.

• Update tools/nixlibs.R to check for libxml2 in with_cloud_support(), turning off the Azure feature flag if libxml2 isn't found.
  • What about configure and configure.win?
  • Is with_cloud_support() the only function that needs changing in tools/nixlibs.R?
• Update the install.Rmd and developers/setup.Rmd vignettes to note that libxml2 is a dependency of Azure (same as with curl and openssl).
• Update DESCRIPTION to include libxml2 in SystemRequirements.