Generate experiment_id and attach to events

[lars-petter-hauge]

Issue Resolves #3720

Approach Generate experiment id, attach to experiment type objects and propagate id as required.

Continued work from: https://github.com/equinor/ert/pull/3729 Depends on: https://github.com/equinor/ert/pull/3793

Pre review checklist

• [x] Added appropriate release note label
• [x] PR title captures the intent of the changes, and is fitting for release notes.
• [x] Commit history is consistent and clean, in line with the contribution guidelines.

Adding labels helps the maintainers when writing release notes. This is the list of release note labels.