GH-50077: [C++][IPC] Avoid int64 overflow in ReadSparseCSXIndex#50038

rok merged 2 commits into

apache:mainapache/arrow:mainfrom

jmestwa-coder:ipc-sparse-csx-index-overflowjmestwa-coder/arrow:ipc-sparse-csx-index-overflowCopy head branch name to clipboard