extract span preparation logic into helper function

[blairhyy-amazon]

Description

Currently, the _patched_api_call method in BotocoreInstrumentor handles the entire span lifecycle (creation, attribute setting, and closure) in a single function. This monolithic approach makes it difficult to extend or customize the instrumentation, particularly when trying to add custom span attributes from the Boto client instance or call context.

This PR proposes to break down _patched_api_call into smaller, more focused helper functions, starting with extracting the span preparation logic. This refactoring will:

1. Improve code maintainability
2. Make it easier to extend the instrumentation through patching
3. Reduce the need for code duplication when customizing span attributes
4. Provide a cleaner interface for future contributors

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• test_botocore_instrumentation.py

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project

[linux-foundation-easycla]

• ✅login: blairhyy-amazon / (e1fc2e1)

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