Backport: [v6.0] fix(openai-compatible): buffer tool call deltas until function.name arrives

[github-actions]

This is an automated backport of #16836 to the release-v5.0 branch. FYI @gr2m
This backport has conflicts that need to be resolved manually.

git cherry-pick output

Auto-merging packages/openai-compatible/src/chat/openai-compatible-chat-language-model.test.ts
CONFLICT (content): Merge conflict in packages/openai-compatible/src/chat/openai-compatible-chat-language-model.test.ts
Auto-merging packages/openai-compatible/src/chat/openai-compatible-chat-language-model.ts
CONFLICT (content): Merge conflict in packages/openai-compatible/src/chat/openai-compatible-chat-language-model.ts
error: could not apply 4d4e1768ea... [v6.0] fix(openai-compatible): buffer tool call deltas until function.name arrives (#16836)
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".
hint: Disable this message with "git config set advice.mergeConflict false"