chore(expect): explicit errorMessage

[dgozman]

This turns an error in the protocol into a successful call with the error message in the new errorMessage field. Existing "element(s) not found" error is migrated to this as well.

Note that expect protocol call may still throw for multiple reasons:

• server connection dropped
• failed to serialize expected/received value, e.g. in toHaveJSProperty()
• unexpected playwright bug

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Strict mode violation

Error: expect(locator).toHaveText(expected) failed

Locator: locator('div')
Expected string: "foo"
Error: strict mode violation: locator('div') resolved to 2 elements:
    1) <div>a</div> aka getByText('a')
    2) <div>b</div> aka getByText('b')

Call log:
  - Expect "toHaveText" with timeout 5000ms
  - waiting for locator('div')

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Invalid selector

Error: expect(locator).toBeVisible() failed

Locator:  ##
Expected: visible
Error: Unexpected token "#" while parsing css selector "##". Did you mean to CSS.escape it?

Call log:
  - Expect "toBeVisible" with timeout 5000ms
  - waiting for ##

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New look for "element(s) not found" error

Error: expect(locator).toBeVisible() failed

Locator:  locator('span')
Expected: visible
Error: element(s) not found
Timeout:  5000ms

Call log:
  - Expect "toBeVisible" with timeout 5000ms
  - waiting for locator('span')

[github-actions]

Test results for "tests 1"

1 failed
❌ [playwright-test] › reporter-html.spec.ts:724 › merged › should warn user when viewing via file:// protocol @macos-latest-node18-2

2 flaky

⚠️ [firefox-library] › library/inspector/cli-codegen-1.spec.ts:1079 › cli codegen › should not throw csp directive violation errors `@firefox-ubuntu-22.04-node18`
⚠️ [firefox-page] › page/page-emulate-media.spec.ts:144 › should keep reduced motion and color emulation after reload `@firefox-ubuntu-22.04-node18`

46752 passed, 819 skipped

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Merge workflow run.