Add docker digest support for Updatecli condition

[olblak]

Add docker digest condition support and fix several regression introduced by #900

• Add support for dockerdigest condition
• dockerimage condition should default to source input if a tag is not defined
• docker image should display information
• Add e2e tests for docker image
• Add e2e tests for docker digest

Test

To test this pull request, you can run the following commands:

go build -o bin/updatecli .
./bin/updatecli diff --config e2e/updatecli.d/success.d/dockerdigest.yaml
./bin/updatecli diff --config e2e/updatecli.d/success.d/dockerimage.yaml 

Additional Information

Tradeoff

Potential improvement