Add the xpack.spaces.defaultSolution for Kibana

[ezimuel]

This PR adds the support of the xpack.spaces.defaultSolution configuration for Kibana (see elastic/kibana#236570).

The proposal is to have the default spaces to Elasticsearch page (es) and the Observability page (oblt) when specifing --edot parameter in start-local.

This should fix #74

[ezimuel]

The xpack.spaces.defaultSolution ENV settings has been distributed with ES 9.1.5. I just tested and it works.

[rogercoll]

Looks great!

side note: We will need to follow up on how to reference the local OTLP endpoint (local edot collector) in the Kibana Observability onboarding instead of the Elasticsearch one

[ezimuel]

Thanks @rogercoll for the review. For the OTLP endpoint, if you want you can open an issue, explaining where the issue is in the Kibana page, thanks.

[alex-fedotyev]

Looks great!

side note: We will need to follow up on how to reference the local OTLP endpoint (local edot collector) in the Kibana Observability onboarding instead of the Elasticsearch one

@rogercoll - did you mean a problem I outlined in #75?
Please, add more details to the issue if you have more specific proposal how to connect onboarding with local collector.