[FR][DAC] Consideration: add exceptions importing from ndjson

[Mikaayenson]

Note: this work will target the DAC-feature branch

related to #3407

---

This is a consideration and not a commitment to work at this point. We should review the feasibility and supportability. If it is doable and not deemed maintainable, we can move the example code to the DAC reference for users to manually implement.

---

Currently in the DAC-feature branch, we can manage exception list using a TOML file structure. When rules are exported/imported into kibana, they are uploaded with the rules using the rules API. This is a one way approach that allows users to manage exception list for DAC.

If users want to preserve their existing exceptions (from Kibana) in VCS using a DAC approach, they would have to manually write the exceptions in our TOML format.

It would be great if we could export exceptions (only ones associated to a detection rule), and import into our TOML format.