`svc package` fails on Request Driven Web Service

[CaptainCarpensir]

When trying to view the template of a RDWS with copilot svc package it currently fails unless you use image.location. This is because when generating the template parameters, the image is not populated correctly by this line.

This results in the error:
✘ generate workload rdws template against environment test: generate stack template parameters: determine image repository type: image is not supported by App Runner:
Because AppRunner validates the image type, this fails when the image is an empty string.

[jorgeavaldez]

Also noting that this command works when it's run via a codepipeline with the buildspec body provided by the pipeline init command