feat(html): allow setting a title to display

[agg23]

Allow the user to display a title in the HTML reporter. It is configured through the main Playwright config:

reporter: [['html', { title: 'Custom test run #1028' }]],

or via the envvar PLAYWRIGHT_HTML_TITLE.

Titles are displayed solely on the root page of the reporter, in the same manner as we display test titles.

The document title is also set to this configured value, if set.

Addresses #35614.

[pavelfeldman]

Please make laser-focused changes that are required for this feature, otherwise it is hard to review / land it.

[github-actions]

Test results for "tests 1"

2 failed
❌ [playwright-test] › runner.spec.ts:118:5 › should ignore subprocess creation error because of SIGINT @macos-latest-node18-1
❌ [webkit-library] › library/browsercontext-device.spec.ts:45:5 › device › should scroll to click @webkit-ubuntu-22.04-node18

5 flaky

⚠️ [chromium-library] › library/chromium/oopif.spec.ts:284:3 › should click @chromium-ubuntu-22.04-node20
⚠️ [firefox-page] › page/page-evaluate.spec.ts:424:3 › should throw for too deep reference chain @firefox-ubuntu-22.04-node18
⚠️ [playwright-test] › ui-mode-test-watch.spec.ts:254:5 › should queue watches @ubuntu-latest-node22-1
⚠️ [webkit-page] › page/page-screenshot.spec.ts:345:5 › page screenshot › should work while navigating @webkit-ubuntu-22.04-node18
⚠️ [playwright-test] › ui-mode-test-watch.spec.ts:145:5 › should watch all @windows-latest-node18-1

39054 passed, 799 skipped
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Merge workflow run.