[Bedrock] Add custom settings model/profile selector

[edelauna]

Which API Provider are you using?

AWS Bedrock

Which Model are you using?

Configured AWS Bedrock account and region

What happened?

Bedrock settings need a provider-specific model/profile selector that can display discovered AWS targets and still support static fallback targets and custom ARNs.

Steps to reproduce

1. Review the Bedrock settings selector changes proposed in [ENHANCEMENT] Improve Amazon Bedrock support #125.
2. Move Bedrock away from the generic model picker.
3. Wire selection through local SettingsView cached state.

Relevant API REQUEST output

N/A

Additional context

Parent issue: #124
Source PR: #125
Story point estimate: 1

Suggested PR group: PR 3 - discovery/settings UI

Acceptance criteria:

• Bedrock settings can select discovered foundation models and inference profiles.
• Custom ARN selection/configuration remains functional.
• Fallback static options are available when discovery fails or is disabled.
• Inputs bind to local cachedState, not live useExtensionState().
• Webview tests cover selection and state wiring.