[C++] Implement a lighter-weight variant #24322
Description
util::variant is an extremely useful structure but its header slows compilation significantly, so using it in public headers is questionable #6545 (comment)
I'll try writing a lighter weight version.
Reporter: Ben Kietzman / @bkietz
Assignee: Ben Kietzman / @bkietz
PRs and other links:
Note: This issue was originally created as ARROW-8113. Please see the migration documentation for further details.