feat(aws): Kendra indexes + data sources

[NitinKumar004]

Summary

Greenfield Amazon Kendra control-plane emulation (Track-1): a drift-free real AWS API for Terraform/SDK clients. Adds aws_kendra_index and aws_kendra_data_source parity. No data plane (no real search/indexing).

Kendra speaks AWS JSON 1.1 dispatched on the X-Amz-Target prefix AWSKendraFrontendService., registered in authzgate.jsonRPCServiceByTarget (so the JSON-RPC gate does not fail closed) — mirroring the aoss template.

Features

• Indexes: CreateIndex, DescribeIndex, UpdateIndex, DeleteIndex, ListIndices
• Data sources: CreateDataSource, DescribeDataSource, UpdateDataSource, DeleteDataSource, ListDataSources
• Resource tags: TagResource, UntagResource, ListTagsForResource (index and data-source ARNs)

Enhancement

• Index (and data source) created synchronously in the ACTIVE state so a Terraform status waiter completes instead of hanging on real Kendra's ~30-minute provisioning.
• Computed fields (index id / data source id / status / createdAt) minted once at create and stored, stable across every Describe/List and after Update. Kendra's API returns no ARN; Terraform derives it from the id, so id stability keeps the arn attribute drift-free.
• Rich nested blocks (server-side encryption, capacity units, document metadata, data source Configuration / VpcConfiguration / CustomDocumentEnrichmentConfiguration) round-trip verbatim as raw JSON so a deeply nested block cannot drift a plan.
• Deleting an index cascades to its data source connectors; a data source requires its parent index (404 otherwise). CUSTOM data sources reject Configuration/RoleArn/Schedule per the real ValidationException rules.
• Snapshottable (identity-preserving) for persistence; generated coverage docs regenerated.

Live e2e (Terraform, hashicorp/aws, kendra endpoint override, port 18059)

• apply: aws_kendra_index DEVELOPER_EDITION + aws_kendra_data_source type=CUSTOM created; index status ACTIVE (no hang, 0s)
• plan -detailed-exitcode: exit 0, no drift on id/arn/status/created_at + config blocks
• update index description: applied in-place, id stable; subsequent plan clean
• destroy: both destroyed; DescribeIndex → ResourceNotFoundException