feat: deprecate toMatchSnapshot for buffers

[dgozman]

These are usually used for screenshots instead of toHaveScreenshot. String-based snapshots are left as is.

---

Also deemphasized toMatchSnapshot throughout all docs.

Fixes #26612.

[github-actions]

Test results for "tests 1"

2 failed
❌ [default] › run-tests.spec.ts:953:5 › should produce output twice
❌ [reuse] › run-tests.spec.ts:953:5 › should produce output twice

7 flaky
⚠️ [chromium] › library/tracing.spec.ts:239:5 › should not include trace resources from the previous chunks
⚠️ [chromium] › page/page-event-request.spec.ts:101:3 › should report navigation requests and responses handled by service worker
⚠️ [chromium] › page/page-event-request.spec.ts:130:3 › should report navigation requests and responses handled by service worker with routing
⚠️ [chromium] › library/tracing.spec.ts:239:5 › should not include trace resources from the previous chunks
⚠️ [chromium] › page/page-event-request.spec.ts:130:3 › should report navigation requests and responses handled by service worker with routing
⚠️ [chromium] › library/tracing.spec.ts:239:5 › should not include trace resources from the previous chunks
⚠️ [chromium] › components/splitView.spec.tsx:65:5 › drag resize

22458 passed, 478 skipped
✔️✔️✔️

❌ [default] › run-tests.spec.ts:953:5 › should produce output twice

Error: expect(received).toBe(expected) // Object.is equality

- Expected  - 0
+ Received  + 1

@@ -9,8 +9,9 @@

      [1/1] test.spec.ts:3:11 › one
      test.spec.ts:3:11 › one
      some output

+     Testing stopped early after 0 maximum allowed failures.
        1 passed (XXms)

    

  969 |
  970 |   const testRun1 = await testController.run(testItems);
> 971 |   expect(testRun1.renderLog({ output: true })).toBe(`
      |                                                ^
  972 |     tests > test.spec.ts > one [2:0]
  973 |       enqueued
  974 |       started

    at /home/runner/work/playwright/playwright/playwright-vscode/tests/run-tests.spec.ts:971:48

❌ [reuse] › run-tests.spec.ts:953:5 › should produce output twice

Error: expect(received).toBe(expected) // Object.is equality

- Expected  - 0
+ Received  + 1

@@ -9,8 +9,9 @@

      [1/1] test.spec.ts:3:11 › one
      test.spec.ts:3:11 › one
      some output

+     Testing stopped early after 0 maximum allowed failures.
        1 passed (XXms)

    

  969 |
  970 |   const testRun1 = await testController.run(testItems);
> 971 |   expect(testRun1.renderLog({ output: true })).toBe(`
      |                                                ^
  972 |     tests > test.spec.ts > one [2:0]
  973 |       enqueued
  974 |       started

    at /home/runner/work/playwright/playwright/playwright-vscode/tests/run-tests.spec.ts:971:48

Merge workflow run.