Add higher frequency equity sampling

[JosueNina]

Description

Previously, drawdown was calculated using the same equity samples as the chart, capped at 4000 points. Now a separate higher frequency series of up to 40000 close price samples is used, improving drawdown accuracy without affecting the chart.

Related Issue

Closes #8699

Motivation and Context

N/A

Requires Documentation Change

N/A

How Has This Been Tested?

It was tested using unit tests.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Refactor (non-breaking change which improves implementation)
• Performance (non-breaking change which improves performance. Please add associated performance test and results)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Non-functional change (xml comments/documentation/etc)

Checklist:

• My code follows the code style of this project.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• My branch follows the naming convention bug-<issue#>-<description> or feature-<issue#>-<description>

[Brnken]

Did I build this

[aiSynergy37]

I investigated the failing Benchmarks job and the instability is concentrated in EmptySingleSecuritySecondEquityBenchmark. I pushed a targeted optimization commit that avoids extra allocations/type checks in Statistics.CalculateDrawdownMetrics while preserving the OHLC drawdown logic from this PR.

Commit: KeerthiCHS@e20ceda
Branch: KeerthiCHS:pr-9354-benchmark-fix

You can apply it on this PR branch with:
git fetch https://github.com/KeerthiCHS/Lean.git pr-9354-benchmark-fix
git cherry-pick e20cedab182160f637af457de0c9b21794bde29a

[aiSynergy37]

I opened a direct helper PR with the benchmark-stability fix from this branch:
#9357

Commit mirrored: e20cedab182160f637af457de0c9b21794bde29a
You can cherry-pick this commit or merge #9357 then merge #9354.

[JosueNina]

Hey @aiSynergy37, thanks for the contribution. I cherry-picked your commit

[jhonabreul]

Thank you!