Read JF_DIST_* env vars

[mickel8]

This PR adds reading old JF env vars related to distribution. This feature will be removed in version 0.8.0.

Besides this, I have also removed divo as it was using non-existing docker compose file, which means that we were not actively running tests with mix test.cluster.

Because of that, I also did a couple of renamings:

• ci.exs -> test_cluster.exs
• test.cluster.ci -> test.cluster.epmd
• test.cluster.dns.ci -> test.cluster.dns

Acknowledging the stipulations set forth:

• [x] I hereby confirm that a Pull Request involving updates to the Software Development Kit (SDK) has been smoothly merged, currently awaits processing, or is otherwise deemed unnecessary in this context.
• [x] I also affirm that another Pull Request, specifically addressing updates to the documentation body (commonly referred to as 'docs'), has either been successfully incorporated, is in the process of review, or is considered superfluous under the prevailing circumstances.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 87.51%. Comparing base (fadf344) to head (d695bfc).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #205 +/- ## ========================================== + Coverage 87.23% 87.51% +0.27% ========================================== Files 74 74 Lines 1536 1538 +2 ========================================== + Hits 1340 1346 +6 + Misses 196 192 -4 ``` | [Files](https://app.codecov.io/gh/fishjam-dev/fishjam/pull/205?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fishjam-dev) | Coverage Δ | | |---|---|---| | [lib/fishjam/application.ex](https://app.codecov.io/gh/fishjam-dev/fishjam/pull/205?src=pr&el=tree&filepath=lib%2Ffishjam%2Fapplication.ex&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fishjam-dev#diff-bGliL2Zpc2hqYW0vYXBwbGljYXRpb24uZXg=) | `48.64% <0.00%> (-2.78%)` | :arrow_down: | ... and [3 files with indirect coverage changes](https://app.codecov.io/gh/fishjam-dev/fishjam/pull/205/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fishjam-dev) ------ [Continue to review full report in Codecov by Sentry](https://app.codecov.io/gh/fishjam-dev/fishjam/pull/205?dropdown=coverage&src=pr&el=continue&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fishjam-dev). > **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fishjam-dev) > `Δ = absolute (impact)`, `ø = not affected`, `? = missing data` > Powered by [Codecov](https://app.codecov.io/gh/fishjam-dev/fishjam/pull/205?dropdown=coverage&src=pr&el=footer&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fishjam-dev). Last update [fadf344...d695bfc](https://app.codecov.io/gh/fishjam-dev/fishjam/pull/205?dropdown=coverage&src=pr&el=lastupdated&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fishjam-dev). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fishjam-dev).