Support 'from' usage in pipeline conditions

[jkljf]

Expected Behavior

On generating the pod for conditions, if 'from' is used for the condition's resource, the pod could mount to that resource (e.g. /pvc/) then copy to condition resource's workspace.
This is similar to Task usage in the pipeline.

Actual Behavior

No support 'from', any Git resource declared for the condition will be handled as normal Git fetch.

Steps to Reproduce the Problem

1. Define a normal Condition check with resource type Git
2. Use that Condition in the pipeline, expect 'from' can be used

Additional Info

[bobcatfish]

Thanks for opening this @jkljf ! I think this is a duplicate of #1256 so I'm going to close it, but I'm going to copy some of your description into there also :D