Centralize Utility methods in ToolDescriptionEvaluator and ToolMetadataExporter

[conniey]

Create common library that uses the same utility methods in both tools:
Comments:

• https://github.com/microsoft/mcp/pull/992/changes#r2515489965
• https://github.com/microsoft/mcp/pull/992/changes#r2688195752
• https://github.com/microsoft/mcp/pull/992/changes#r2688200225
• https://github.com/microsoft/mcp/pull/992/changes#r2515489944