Backend: Add devfile_operations module to handle devfile validation specific code

MR: Introduce devfile operations module (!192495 - merged)

Description

Introduce a devfile_operations module containing the backend code that will be triggered by GraphQL.

Acceptance criteria

• Extract the code from workspace create logic which validates the devfile to this new module.
• Use this module files in workspace create logic to validate the devfile.
• Wrap the devfile errors in workspace create logic to effectively track it.

Implementation plan

See above.