[Bicep Child Module Proposal]: `avm/res/cognitive-services/account/deployment`

### Check for previous/existing GitHub issues/module proposals

- [x] I have checked for previous/existing GitHub issues/module proposals.

### Check this module doesn't already exist in the module indexes

- [x] I have checked for that this module doesn't already exist in the module indexes.

### Do you want to add new functionality to an existing module, publish an existing child module or both?

The functionality exists already and I want to make it available as a published child module independent from its parent module

### Parent module?

avm/res/cognitive-services/account

### Module Name

avm/res/cognitive-services/account/deployment

### Module Details

This proposal requests onboarding and publication of the existing Cognitive Services account deployment child module:

`avm/res/cognitive-services/account/deployment`

The child module implements the resource type:

`Microsoft.CognitiveServices/accounts/deployments`

The implementation was introduced in Azure/bicep-registry-modules PR #7207, where the deployment resource was extracted from the parent Cognitive Services account module into a dedicated child module.

Publishing it independently would allow consumers to manage model deployments separately from the lifecycle of the parent Cognitive Services account. This is useful for scenarios where model deployments are added, upgraded, scaled, or removed independently from the account itself.

The module supports the existing deployment capabilities exposed by the parent module, including:

- Model name, format, and version
- Deployment SKU and capacity
- Version upgrade options
- RAI policy configuration
- Optional `modelProviderData` required for partner models such as Anthropic Claude
- Backward compatibility for deployments that do not require provider attestation

The `modelProviderData` capability addresses a real provisioning gap identified while deploying Anthropic models through Azure AI Foundry. Related work includes:

- Azure/bicep-registry-modules#7207 — child module extraction
- Azure/bicep-registry-modules#7199 — `modelProviderData` support
- Azure/azure-rest-api-specs#44944 — corresponding REST API specification contribution
- Azure/azure-rest-api-specs#43610 — original API specification gap

The child module already exists in source and is used internally by the parent account module. The remaining work is to complete the AVM child-module publishing and onboarding requirements.

I am willing to contribute the onboarding implementation and help maintain the module.

Start with the existing avm/res/cognitive-services/account/deployment child module and review Azure/bicep-registry-modules PR #7207, then check the AVM child-module publishing and onboarding requirements. Confirm that the Microsoft.CognitiveServices/accounts/deployments module can be published independently while retaining the listed deployment and modelProviderData capabilities and parent-module compatibility.

Written by the indexing model from the issue text.