Add Ballista 55.0.0 release post

[andygrove]

Summary

• announce Apache DataFusion Ballista 55.0.0
• highlight AQE, Flight SQL/ADBC, job history, range shuffles, and runtime improvements
• compare TPC-H SF1000 performance with Spark 4.1.3 and Spark 4.1.3 + Comet 1.1.0, using the numbers from the benchmarking guide, with the caveats, and the improvement on main since the benchmark runner started declaring partition columns (perf(bench): register Hive partition columns in the TPC-H runner datafusion-ballista#2553, #2563)
• drop the single-executor SF10 AQE result
• link to the full changelog and previous Ballista release post

The headline Ballista numbers (502.4 s) are from c76278cd, where the benchmark runner declares the partition columns. That commit is after the release and also includes a few engine changes. The post gives the 55.0.0 runner's total (571.6 s) for comparison.

Validation

• git diff --check
• local site build not run (content-only change)

[villebro]

LGTM