chore: implement integration tests for resources

[LucaButBoring]

Implements basic integration tests for resources and resource templates. Just helps to ensure things don't fall too far out of step with the upstream protocol. Resource subscriptions are supported by @modelcontextprotocol/everything, but are not tested here due to lacking client support (#251).

Motivation and Context

Avoids regressions against the protocol.

How Has This Been Tested?

This PR only adds integration tests.

Breaking Changes

N/A

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

[tzolov]

Thanks @LucaButBoring!
I've reviewed the listResources/readResource test coverage across all transports. While we already have listResources test coverage, the async readResource testing was previously disabled.
The issue was that nesting StepVerifier instances within loops creates problems for reactive pipelines, so I had to implement a different approach.
I've submitted PR #314 that generalizes the listResources/readResource testing across all supported client transports. Please feel free to review when you have a chance.

[tzolov]

This PR is replaced by more generic implementation: #314