feat (ai): add array support to stopWhen (#6339)

## Background

When an additional stop condition such as `hasToolCall` is used, it
makes sense to still keep a step limit condition in case the additional
condition is never met to prevent infinite loops.

## Summary

Add support for multiple stop conditions passed as an array with `or`
semantics. When any stop condition is met, the multi-step loop is
aborted.

## Tasks

- [x] implementation
- [x] add tests
- [x] changeset update
- [x] jsdoc
- [x] extract

Author: lgrammel

.changeset/chatty-steaks-search.md

@@ -0,0 +1,5 @@
+---
+'ai': patch
+---
+
+feat (ai): add array support to stopWhen

packages/ai/core/generate-text/__snapshots__/generate-text.test.ts.snap

@@ -1,6 +1,6 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
-exports[`options.maxSteps > 2 steps: initial, tool-result > onStepFinish should be called for each step 1`] = `
+exports[`options.stopWhen > 2 steps: initial, tool-result > onStepFinish should be called for each step 1`] = `
 [
   DefaultStepResult {
     "content": [
@@ -133,7 +133,7 @@ exports[`options.maxSteps > 2 steps: initial, tool-result > onStepFinish should
 ]
 `;
 
-exports[`options.maxSteps > 2 steps: initial, tool-result > result.response.messages should contain response messages from all steps 1`] = `
+exports[`options.stopWhen > 2 steps: initial, tool-result > result.response.messages should contain response messages from all steps 1`] = `
 [
   {
     "content": [
@@ -171,7 +171,7 @@ exports[`options.maxSteps > 2 steps: initial, tool-result > result.response.mess
 ]
 `;
 
-exports[`options.maxSteps > 2 steps: initial, tool-result > result.steps should contain all steps 1`] = `
+exports[`options.stopWhen > 2 steps: initial, tool-result > result.steps should contain all steps 1`] = `
 [
   DefaultStepResult {
     "content": [
@@ -304,7 +304,7 @@ exports[`options.maxSteps > 2 steps: initial, tool-result > result.steps should
 ]
 `;
 
-exports[`options.maxSteps > 2 steps: initial, tool-result with prepareStep > onStepFinish should be called for each step 1`] = `
+exports[`options.stopWhen > 2 steps: initial, tool-result with prepareStep > onStepFinish should be called for each step 1`] = `
 [
   DefaultStepResult {
     "content": [
@@ -437,7 +437,7 @@ exports[`options.maxSteps > 2 steps: initial, tool-result with prepareStep > onS
 ]
 `;
 
-exports[`options.maxSteps > 2 steps: initial, tool-result with prepareStep > result.response.messages should contain response messages from all steps 1`] = `
+exports[`options.stopWhen > 2 steps: initial, tool-result with prepareStep > result.response.messages should contain response messages from all steps 1`] = `
 [
   {
     "content": [
@@ -475,7 +475,7 @@ exports[`options.maxSteps > 2 steps: initial, tool-result with prepareStep > res
 ]
 `;
 
-exports[`options.maxSteps > 2 steps: initial, tool-result with prepareStep > result.steps should contain all steps 1`] = `
+exports[`options.stopWhen > 2 steps: initial, tool-result with prepareStep > result.steps should contain all steps 1`] = `
 [
   DefaultStepResult {
     "content": [