GH-48435: [Ruby] Add support for reading sparse union array

[kou]

Rationale for this change

It's a sparse variant of union array.

What changes are included in this PR?

• Add ArrowFormat::SparseUnionType
• Add ArrowFormat::SparseUnionArray

Are these changes tested?

Yes.

Are there any user-facing changes?

Yes.

• GitHub Issue: [Ruby] Add support for reading sparse union array #48435

[github-actions]

⚠️ GitHub issue #48435 has been automatically assigned in GitHub to PR creator.

[hiroyuki-sato]

+1

LD_LIBRARY_PATH=/tmp/local/lib GI_TYPELIB_PATH=/tmp/local/lib/girepository-1.0 rake test
cd /path/to/arrow/ruby/red-arrow-format
/path/to/.rbenv/versions/3.4.7/bin/ruby test/run.rb
Loaded suite test
Started
/home/arch/arrow/ruby/red-arrow-format/lib/arrow-format/file-reader.rb:65: warning: IO::Buffer is experimental and both the Ruby and C interface may change in the future!
Finished in 0.244041104 seconds.
------------------------------------------------------------------------------------------------------------------------
17 tests, 17 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed
------------------------------------------------------------------------------------------------------------------------
69.66 tests/s, 69.66 assertions/s
cd -