fix: align benchmark runtimes with project target frameworks

[LeeCampbell]

Summary

• Removed 7 obsolete benchmark runtime jobs (Net481 LegacyJit/RyuJit, Core 2.1, 3.1, 5.0, 6.0, 7.0) that no longer match the project's target frameworks
• Added missing net9.0 and net10.0 jobs to match the csproj's TargetFrameworks (net8.0;net9.0;net10.0)

Test plan

• dotnet build HdrHistogram.Benchmarking/ succeeds with 0 errors
• dotnet format HdrHistogram.Benchmarking/ --verify-no-changes passes
• Run benchmarks locally to confirm all three runtimes execute correctly

🤖 Generated with Claude Code

[LeeCampbell]

Benchmark Results — Updated Runtime Config

Environment: BenchmarkDotNet v0.15.8, Windows 11, Intel Core i5-14400 2.50GHz, 16 logical / 10 physical cores
.NET SDK 10.0.104 — runtimes: .NET 8.0.25, .NET 9.0.14, .NET 10.0.4

LeadingZeroCount 64-Bit

Full results (click to expand)

Method	Runtime	Mean	Error	StdDev	Op/s	Ratio
CurrentImplementation	.NET 8.0	0.4212 ns	0.0085 ns	0.0107 ns	2,374,134,286.7	1.00
CurrentImplementation	.NET 9.0	0.4347 ns	0.0074 ns	0.0088 ns	2,300,697,013.7	1.00
CurrentImplementation	.NET 10.0	0.4199 ns	0.0037 ns	0.0035 ns	2,381,356,428.1	1.00

LeadingZeroCount 32-Bit

Full results (click to expand)

Method	Runtime	Mean	Error	StdDev	Op/s	Ratio
CurrentImplementation	.NET 8.0	0.4305 ns	0.0036 ns	0.0032 ns	2,322,925,901.9	1.00
CurrentImplementation	.NET 9.0	0.4381 ns	0.0083 ns	0.0078 ns	2,282,460,547.5	1.00
CurrentImplementation	.NET 10.0	0.4343 ns	0.0074 ns	0.0085 ns	2,302,434,700.4	1.00

Recording 32-Bit

Method	Runtime	Mean	Op/s	Ratio
LongHistogramRecording	.NET 8.0	1.677 ns	596,146,928.2	1.00
LongHistogramRecording	.NET 9.0	1.528 ns	654,455,498.1	1.00
LongHistogramRecording	.NET 10.0	1.767 ns	565,886,595.3	1.00
IntHistogramRecording	.NET 8.0	1.402 ns	713,181,057.3	0.84
IntHistogramRecording	.NET 9.0	1.295 ns	772,060,501.0	0.85
IntHistogramRecording	.NET 10.0	1.329 ns	752,385,018.9	0.75
ShortHistogramRecording	.NET 8.0	1.493 ns	669,787,728.5	0.89
ShortHistogramRecording	.NET 9.0	1.223 ns	817,436,327.0	0.80
ShortHistogramRecording	.NET 10.0	1.203 ns	831,437,495.2	0.68

Note: The ByteBuffer benchmark report in the artifacts is from a prior run with the old (stale) runtime config — all non-installed runtimes show NA. It will need to be re-run once the ByteBuffer benchmark branch is rebased onto this fix.

All three existing benchmark suites ran successfully across .NET 8.0, 9.0, and 10.0 with the updated runtime configuration.