fix(mcptools): always emit mcp.method.name attribute on MCP tracing spans

[Aryanbhargava18]

Which problem is this PR solving?

Resolves #9748

In cmd/jaeger/internal/extension/jaegerquery/internal/mcptools/middleware.go, otelsemconv.McpMethodName(method) was previously only appended inside the else block when toolName == "". As a result, tool execution requests (tools/call) recorded gen_ai.operation.name and gen_ai.tool.name, but omitted mcp.method.name.

Per the OpenTelemetry GenAI Semantic Conventions for MCP server spans, mcp.method.name is marked as Required on all MCP spans (including tools/call). Furthermore, the specification explicitly notes:

"Populating this attribute for tool calling along with mcp.method.name allows consumers to treat MCP tool calls spans similarly with other tool call types."

This also aligns the tracing middleware with TestMetricsMiddlewareToolCallSuccess in the same package, which already asserts both gen_ai.tool.name and mcp.method.name.

Description of the changes

• Initialize attrs with otelsemconv.McpMethodName(method) in createTracingMiddleware so it is unconditionally recorded on all MCP spans.
• Update TestTracingMiddlewareToolCallSuccess in middleware_test.go to assert the presence of mcp.method.name.

How was this change tested?

• Unit tests in cmd/jaeger/internal/extension/jaegerquery/internal/mcptools/middleware_test.go.