Fix analyzer warnings in Benchmarking and Examples projects

[LeeCampbell]

Summary

The CI build reports 10 analyzer warnings in the HdrHistogram.Benchmarking and HdrHistogram.Examples projects.
These are pre-existing and not introduced by any recent PR.

Warnings

CA1852 — Type can be sealed (×2)

• HdrHistogram.Benchmarking/Program.cs#L9
• HdrHistogram.Examples/Program.cs#L3

CA1707 — Remove underscores from member/type names (×6)

• LeadingZeroCountBenchmarkBase.BBarry_imp1() — line 189
• LeadingZeroCountBenchmarkBase.BBarry_imp2() — line 199
• LeadingZeroCountBenchmarkBase.BBarry_imp3() — line 209
• LeadingZeroCountBenchmarkBase.BBarry_imp4() — line 219
• BBarry32BitIfShiftLookupWith64BitShiftBranch_2 — line 46
• BBarry32BitIfShiftLookupWith64BitShiftBranch_3 — line 79

CA1829 — Use Length instead of Count() (×1)

• LeadingZeroCountBenchmarkBase.cs#L42

Notes

All warnings are in the benchmarking and examples projects, not the main library.
The underscore names (BBarry_imp*) reference a contributor's implementation variants used for comparative benchmarking — renaming should preserve the intent of identifying the author/variant.

Reference

• Observed in PR chore(#161): Drop netstandard2.0 target, support net8.0+ only #164 build annotations