Backport: feat(provider/anthropic): support fine-grained tool streaming with eagerInputStreaming

[vercel-ai-sdk]

This is an automated backport of #13078 to the release-v5.0 branch. FYI @sylviezhang37
This backport has conflicts that need to be resolved manually.

git cherry-pick output

CONFLICT (file location): examples/ai-functions/src/stream-text/anthropic/fine-grained-tool-streaming.ts added in 3fb4e7073 (feat(provider/anthropic): support fine-grained tool streaming with eagerInputStreaming (#13078)) inside a directory that was renamed in HEAD, suggesting it should perhaps be moved to examples/ai-core/src/stream-text/fine-grained-tool-streaming.ts.
Auto-merging packages/anthropic/src/anthropic-messages-api.ts
CONFLICT (content): Merge conflict in packages/anthropic/src/anthropic-messages-api.ts
Auto-merging packages/anthropic/src/anthropic-messages-language-model.test.ts
Auto-merging packages/anthropic/src/anthropic-prepare-tools.test.ts
Auto-merging packages/anthropic/src/anthropic-prepare-tools.ts
CONFLICT (content): Merge conflict in packages/anthropic/src/anthropic-prepare-tools.ts
error: could not apply 3fb4e7073... feat(provider/anthropic): support fine-grained tool streaming with eagerInputStreaming (#13078)
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"