fea: Functional tests for RAG - #3051

Adds RAG workflow to functional tests for all the managed paths:

• from user documents
• from taxonomy files
• from processed taxonomy files

Testing logic emulates the e2e-custom.sh script defined in PR #2948, with changes specific to the functional test environment.

Notes:

• This change has an impact on the overall execution tim of the functional tests, because it runs an additional ilab data generate command to process the knowledge documents.
• The test temporarily overrides the required env var to enable the RAG feature and runs on every CI execution: this is the main difference from the e2e-custom.sh script that instead runs from a custom job.

Issue resolved by this Pull Request:
Resolves #3033

Checklist:

• Commit Message Formatting: Commit titles and messages follow guidelines in the
  conventional commits.
• Changelog updated with breaking and/or notable changes for the next minor release.
• Documentation has been updated, if necessary.
• Unit tests have been added, if necessary.
• Functional tests have been added, if necessary.
• E2E Workflow tests have been added, if necessary.