Allow setting summary statistics during Initialize

[Martin-Molinero]

Description

QCAlgorithm.SetSummaryStatistic now keeps statistics set before the statistics service is attached, and SetStatisticsService applies them once the result handler provides the service. Previously the call dereferenced a null _statisticsService.

Related Issue

Closes #9853

Motivation and Context

The statistics service is attached in the result handler's SetAlgorithm, which Engine.Run calls after Setup.Setup(...) has already executed Initialize(), so calling SetSummaryStatistic / set_summary_statistic from Initialize failed with Object reference not set to an instance of an object.

Requires Documentation Change

No

How Has This Been Tested?

Extended the StatisticsResultsAlgorithm regression (C# and Python) to set a summary statistic in Initialize and assert it is present in Statistics.Summary at OnEndOfAlgorithm. Both variants fail with the reported null reference without the fix and pass with it.

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>

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