Devfile components sync support

[rajivnathan]

Related to #2470

• Implement source syncing to containers within a fat pod.
• Ignore files in .gitignore
• Sync delta changes instead of entire source

[rajivnathan]

/area devfile

[johnmcollier]

/assign @johnmcollier

[johnmcollier]

As discussed on the odo dev meeting today:

• We'll keep the existing watch and sync technology, it works fine as-is, and should work well with Devfile projects
• Current sync function can only sync to one container
• As Devfile projects may deploy fat / multi-container pods, we may need to sync the source code to multiple containers, so need to modify the sync function to support that
  • However, we don't want to sync to every container
• We'll use the mountsources field in the devfile to determine which containers need access to the source code, and have a single shared volume with the source that those containers would mount
  • Means we only need to sync once

[johnmcollier]

Updating the plan for Devfile syncing:

• When creating the deployment for devfiles, create an emptyDir volume and mount it under /projects
  • /projects is the default mount path for projects in Che with devfiles
• If a component has mountSources: true set in it, we'll mount the emptyDir volume to it
• When syncing, we'll sync the source code to the first container we found that had set mountSources: true.
  • No need to sync across the other containers since they will be sharing the same volume.