feature: add support `ResourceTemplates` to `mcptest` package

[Slach]

Problem Statement

I want to test server.MCPServer which have following code fragment

	// Table Structure Template Resource
	tableTemplate := mcp.NewResourceTemplate(
		"clickhouse://table/{table_name}",
		"Table Structure",
		mcp.WithTemplateDescription("Detailed structure information for a specific table"),
		mcp.WithTemplateMIMEType("application/json"),
	)

	srv.AddResourceTemplate(tableTemplate, func(ctx context.Context, req mcp.ReadResourceRequest) ([]mcp.ResourceContents, error) {
		// Extract table name from URI
		uri := req.Params.URI
		parts := strings.Split(uri, "/")
		if len(parts) < 3 {
			return nil, fmt.Errorf("invalid table URI format")
		}
		tableName := parts[len(parts)-1]

		log.Debug().Str("table", tableName).Msg("Reading table structure resource")

		columns, err := chClient.DescribeTable(ctx, tableName)
		if err != nil {
			return nil, fmt.Errorf("failed to get table structure: %w", err)
		}

		jsonData, err := json.MarshalIndent(columns, "", "  ")
		if err != nil {
			return nil, fmt.Errorf("failed to marshal table structure: %w", err)
		}

		return []mcp.ResourceContents{
			mcp.TextResourceContents{
				URI:      uri,
				MIMEType: "application/json",
				Text:     string(jsonData),
			},
		}, nil
	})

Proposed Solution

Add something like that

func (s *mcptest.Server) AddResourceTemplate(template mcp.ResourceTemplate, handler server.ResourceTemplateHandlerFunc) {

}