fix(expect): name matcher in toMatchObject failure message

[fibibot]

Summary

expect(received).toMatchObject(expected) previously failed with
AssertionError: Values are not equal., and the .not.toMatchObject
branch produced Expected actual: ... not to be: .... Both are
misleading because toMatchObject is a superset check, not strict
equality.

The triggerError closure in expect/_matchers.ts reused
buildEqualErrorMessage / buildNotEqualErrorMessage from
expect/_build_message.ts. This change adds two matcher-specific
builders, buildToMatchObjectErrorMessage and
buildNotToMatchObjectErrorMessage, that emit Jest-style headers:

expect(received).toMatchObject(expected)

<diff>

expect(received).not.toMatchObject(expected)

Expected: not <expected>
Received: <received>

Both branches of toMatchObject are routed through the new builders.
The diff content (already trimmed to the subset by PR #7078) is
preserved.

Test plan

• Updated expect/_to_match_object_test.ts "throws the correct
  error messages" case to assert on the new matcher-named prefix
  and explicitly reject the previous Values are not equal /
  not to be phrasings.
• deno fmt --check passes for expect/.
• deno lint passes for expect/.
• deno test -A expect/ passes (167 passed, 0 failed).
• Reproduced the original issue locally; failure message now reads
  expect(received).toMatchObject(expected) instead of Values are not equal..

Closes #6999
Closes bartlomieju/orchid-inbox#90

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[codecov]

Codecov Report

❌ Patch coverage is 87.87879% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.60%. Comparing base (5ea9159) to head (d0288ca).

Files with missing lines	Patch %	Lines
expect/_build_message.ts	85.18%	0 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7142      +/-   ##
==========================================
- Coverage   94.61%   94.60%   -0.01%     
==========================================
  Files         634      634              
  Lines       51830    51860      +30     
  Branches     9341     9345       +4     
==========================================
+ Hits        49037    49063      +26     
  Misses       2218     2218              
- Partials      575      579       +4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.