Restructure Dapr Agents integrations and document Drasi extension

[JeffreyJPZ]

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Description

• Restructures Dapr Agents integrations docs so integrations are searchable by provider (e.g. Drasi) and type (loaders, splitters, vector stores, tools, etc.)
• Adds an entry in the integrations docs for the Drasi extension + the Drasi change-driven agents example in the quickstarts docs
• Adds missing examples to the quickstarts docs

This should make it a little less painful to document the other integrations that are currently missing (embeddings, executors, chat clients, etc.) and other integrations in the future (trigger sources maybe).

Issue reference

Closes #5252