Adding strategy for migrating Duo Chat tools to blueprint

Why is this change being made?

Architectural Blueprint for Prompts Migration (!7311 - merged) adds a blueprint for prompt migration. It contains Design and implementation details section that lists strategies per-feature. Currently, it's Code Completion and Code Generations.

This MR adds a strategy for Duo Chat tools migration.

PoC:

• Execute Duo Chat explain code tool via agents (gitlab-org/gitlab!160252 - merged)
• feat(agents): add prompts for explain code tool (gitlab-org/modelops/applied-ml/code-suggestions/ai-assist!1132 - merged)

Commits

• Adding strategy for migrating Duo Chat tools to blueprint

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