Foundry Classic (v1) Agents: widen mcp_list_tools to allow arbitrary schema items

[trrwilson]

The mcp_list_tools schema component used in run step details has inappropriately specified a narrowly defined item schema for its tools property array elements. These property values are ultimately at the discretion of the MCP tools being used and this has resulted in validation errors when non-conforming tool representations didn't parse in the restricted schema.

This change replaces the Record<ActivityFunctionDefinition> previously used with an open-ended Record<unknown>, also removing the otherwise unused schema components.

[github-actions]

Next Steps to Merge

Next steps that must be taken to merge this PR:

• ❌ This PR targets either the main branch of the public specs repo or the RPSaaSMaster branch of the private specs repo. These branches are not intended for iterative development. Therefore, you must acknowledge you understand that after this PR is merged, the APIs are considered shipped to Azure customers. Any further attempts at in-place modifications to the APIs will be subject to Azure's versioning and breaking change policies. Additionally, for control plane APIs, you must acknowledge that you are following all the best practices documented by ARM at aka.ms/armapibestpractices. If you do intend to release the APIs to your customers by merging this PR, add the PublishToCustomers label to your PR in acknowledgement of the above. Otherwise, retarget this PR onto a feature branch, i.e. with prefix release- (see aka.ms/azsdk/api-versions#release--branches).
• ❌ This PR has at least one change violating Azure versioning policy (label: VersioningReviewRequired).
  To unblock this PR, either a) introduce a new API version with these changes instead of modifying an existing API version, or b) follow the process at aka.ms/brch.
• ❌ The required check named Swagger BreakingChange has failed. To unblock this PR, follow the process at aka.ms/brch.

Comment generated by summarize-checks workflow run.

[github-actions]

API Change Check

APIView identified API level changes in this PR and created the following API reviews

Language	API Review for Package
TypeSpec	Azure.AI.Agents
JavaScript	@azure/ai-agents
Python	azure-ai-agents