feat(locator handler): perform checkpoit during locator.waitFor

[dgozman]

Fixes #32255.

[github-actions]

Test results for "tests 1"

2 failed
❌ [installation tests] › playwright-electron-should-work.spec.ts:31:5 › electron should work with special characters in path
❌ [playwright-test] › babel.spec.ts:135:5 › should not transform external

4 flaky

⚠️ [playwright-test] › ui-mode-test-setup.spec.ts:98:5 › should show errors in config
⚠️ [playwright-test] › ui-mode-test-attachments.spec.ts:102:5 › should linkify string attachments
⚠️ [webkit-page] › page/page-goto.spec.ts:301:3 › should fail when navigating to bad SSL
⚠️ [playwright-test] › ui-mode-test-watch.spec.ts:145:5 › should watch all

35506 passed, 659 skipped
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Merge workflow run.