Azure Search: Data-Plane 2026-08-01-Preview (#44399)

* Initial PR for Search  DP 2026-08-01-preview

* Sync Azure Search data-plane spec from AzureSearch (tsp/2026-08-01-preview@c9860b08ce0)

* Add new version to dp readme

* Fix example errors

* Fix bug: unexpected removal of import client.tsp

* Fix typespec validation errors

* Sync Azure Search data-plane spec from AzureSearch (tsp/2026-08-01-preview@112598ffe6f)

* remove examples of reverted feature

* Sync Azure Search data-plane spec from AzureSearch (tsp/2026-08-01-preview@efab4a0a9b6)

* Sync Azure Search data-plane spec from AzureSearch (tsp/2026-08-01-preview@6daea4de446)

* Sync from azs

* Sync Azure Search data-plane spec from AzureSearch (tsp/2026-08-01-preview@24bf4a5b600)

* Sync Azure Search data-plane spec from AzureSearch (tsp/follow-up@a0fde64bdb1)

* Sync Azure Search data-plane spec from AzureSearch (tsp/follow-up@3aa88617631)

* Sync Azure Search data-plane spec from AzureSearch (tsp/late-sync@f8c7d0c3a5b)

* Sync Azure Search data-plane spec from AzureSearch (tsp/late-sync@3a7294ec6c6)

* Remove SDK emitter API version pin

* Sync Azure Search data-plane spec from AzureSearch (tsp/late-sync@8f059cbe010)

* Sync tsp fixes from azs

* Fix service.yaml

* [Search] Fixes for 2026-08-01-preview TSP (#45308)

* Update 1

* Update 2

* Reffactor spec multipart

* Force generator to create models for SDKs and fix string output

* Undo

* Content dispostion customizations

* Add missing namespace customizations

* Resolve merge conflicts

* Remove convenience/protocol customizations

* Fix tsv and tsp format for 1.15: csharp model suffix customizations

* Revert "Fix tsv and tsp format for 1.15: csharp model suffix customizations"

This reverts commit 8bb63059b0817193171bff30ad6a0be50170d5bd.

* Tsp format

* Remove unexpected annotations

* Suppress model suffix errors from tsv (tsp compiler 1.15.0)

* Fix KnowledgeBaseActivityRecordModel.modelName as required

* Update ServedImage properties; Remove KnowledgeBaseRetrievalEventStreamResponse

* Update changelog (no spec change)

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Co-authored-by: efrainretana <efrainretana@microsoft.com>
Co-authored-by: efrainretana <141282336+efrainretana@users.noreply.github.com>