Move add binding

[wild-endeavor]

• Move the artifact related stuff out of identifier.proto into its own file.
• Renamed the PartitionValue message to LabelValue and use it in both Partitions and Tag
• LabelValue is now a oneof a static value, an artifact binding data (which is used for triggers) and a new message InputBindingData which is the replacement for the template strings.
  • In the future, if we want to support bindings to outputs of arbitrary tasks for workflow partition values or tag values, we can create a new node binding data message, or repurpose this one and add a node id.
• Remove the oneof for the source in ArtifactSpec - an artifact can have all three of task execution, workflow execution and principal.
• Add a metadata type alongside the metadata.

[codecov]

Codecov Report

All modified lines are covered by tests ✅

❗ No coverage uploaded for pull request base (artifacts@4854ce7). Click here to learn what that means.

❗ Current head 5bb2167 differs from pull request most recent head 975a3fb. Consider uploading reports for the commit 975a3fb to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##             artifacts     #452   +/-   ##
============================================
  Coverage             ?   78.48%           
============================================
  Files                ?       18           
  Lines                ?     1250           
  Branches             ?        0           
============================================
  Hits                 ?      981           
  Misses               ?      212           
  Partials             ?       57           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.