SDK generation workflow: Do not use nested TypeSpec config path

GitHub agent workflow for SDK generation should not explore the spec path to find the tspconfig.yaml if a tspconfig.yaml is found in the given TypeSpec project path. It should search for a TypeSpec project path only and only if a tspconfig.yaml is not found in the given path. SDK generation should be triggered using the given TypeSpec path by user if tspconfig.yaml exists in the path, to avoid using incorrect tspconfig.yaml when a project contains tspconfig.yaml in multiple sub directory. For e.g. `https://github.com/Azure/azure-rest-api-specs/blob/main/specification/compute/resource-manager/Microsoft.Compute/Compute/`