feat(benchmarks): add Jackson Blackbird JSON mode

[chaokunyang]

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• Substantial AI assistance was used in this PR: yes / no
• If yes, I included a completed AI Contribution Checklist in this PR description and the required AI Usage Disclosure.
• If yes, my PR description includes the required ai_review summary and screenshot evidence or equivalent persisted links of the final clean AI review results from both fresh reviewers described in AI_POLICY.md, the Fory-guided reviewer and the independent general reviewer, on the current PR diff or current HEAD after the latest code changes.

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• Does this PR introduce any public API change?
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Benchmark

[chaokunyang]

Jackson and Jackson Blackbird Benchmark Comparison

Environment and methodology

• Platform: Apple M4 Pro, 12 cores, 48 GB RAM, macOS 15.7.2 arm64
• JDK: 26.0.1
• JMH: 1.37
• Benchmark JAR SHA-256:
  4ac05586cbcec971f52ce804a03c3cc00d46c0bc89668ba1c22470c2845d9c75
• Workload: the same MediaContent JSON fixture for every implementation
• Warmup: 3 iterations × 2 seconds
• Measurement: 5 iterations × 2 seconds
• Forks: 1
• Threads: 1
• Mode: throughput in operations per second; higher is better

First run: Jackson Blackbird

Command:

cd benchmarks/java
./run_json.sh --skip-build --jackson blackbird \
  --reports-dir ../../tasks/task-java-json-blackbird/published-blackbird

Representation	Operation	fory-json ops/sec	Jackson Blackbird ops/sec	Gson ops/sec	Fastest
String	Serialize	7,033,317	2,144,424	1,018,621	fory-json
String	Deserialize	3,176,133	1,072,902	795,836	fory-json
UTF-8 bytes	Serialize	9,866,897	1,971,515	1,001,983	fory-json
UTF-8 bytes	Deserialize	3,123,599	1,314,077	884,427	fory-json

Raw JMH result SHA-256:
337cfc849e96da1727943d2993901d91f4f11bf71fe6510869a8b560658bd9bf.

Second run: ordinary Jackson

Command:

cd benchmarks/java
./run_json.sh --skip-build --jackson standard \
  --reports-dir ../../tasks/task-java-json-blackbird/published-standard

Representation	Operation	fory-json ops/sec	Jackson ops/sec	Gson ops/sec	Fastest
String	Serialize	7,042,926	1,956,691	999,161	fory-json
String	Deserialize	2,884,851	1,045,016	865,033	fory-json
UTF-8 bytes	Serialize	9,838,225	1,703,997	966,242	fory-json
UTF-8 bytes	Deserialize	3,066,469	1,212,879	891,051	fory-json

Raw JMH result SHA-256:
cf8d12715b33df34ef663fc1bdbee6bcb07576933117ee18f31278137762c436.

Ordinary Jackson versus Jackson Blackbird

The improvement is calculated as (Blackbird throughput / Jackson throughput - 1) × 100%.

Representation	Operation	Jackson ops/sec	Jackson Blackbird ops/sec	Difference ops/sec	Blackbird improvement
String	Serialize	1,956,691	2,144,424	+187,733	+9.59%
String	Deserialize	1,045,016	1,072,902	+27,887	+2.67%
UTF-8 bytes	Serialize	1,703,997	1,971,515	+267,519	+15.70%
UTF-8 bytes	Deserialize	1,212,879	1,314,077	+101,198	+8.34%

The geometric-mean improvement across the four throughput ratios is 8.98%. The String
deserialization difference is small relative to the JMH-reported score-error ranges, so additional
paired runs would be needed to establish that individual 2.67% delta with high confidence.