Deprecate old experiments in favor of new code

[aittalam]

The purpose of this issue is to completely replace the old code for /experiments with the new one. For this reason it
depends on #570, #571, and #572, ie. it needs the new endpoint to be fully compatible, API-wise, with the previous version.

This brings in the missing switch that was initially expected in #479 , namely:

• a workflow that uses those independent jobs (Workflow using independent inference and evaluation, without annotation service #485 ):
  • an inference job using the specified model and parameters: Batch inference round 1/n #309 (and Add support for seq2seq models with transformers or vLLM as-a-library #339 for seq2seq models)
  • an independent evaluation job, instead of one that bundles inference: Evaluation as a stand-alone job over data, not the trigger for multiple jobs #435

Additionally, we need to:

• rename eval_lite to evaluation
• switch experiment_new to experiment
• remove old evaluation code
• tests (all CI AND manual tests with UI)