Prevent QuantBook composer reset on notebook initialization

[jhonabreul]

Description

Introduce new static flag HandlersInitialized to the QuantBook class so that it is prevented from resetting the composer on first creation, since the notebook initializers will set it to true after they initialize the composer and the Lean system and algorithm handlers.

Related Issue

Closes #8375

Motivation and Context

Requires Documentation Change

How Has This Been Tested?

Research notebooks

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>