Rationalize versioning of dependencies and applications

[Annopaolo]

• Make Elixir 1.15[.7] and Erlang/OTP 25.3.2[.7] the only language versions used in apps, tools and CI
• Update astarte dependencies (astarte_core, astarte_rpc, astarte_data_access) to the latest master (1.2.0-dev) version for all Astarte apps
• Update tools to use hexpm/elixir images where needed
• Fix some typos in GH docs workflow

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (95fd1a2) 81.92% compared to head (350f867) 68.27%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #878 +/- ## =========================================== - Coverage 81.92% 68.27% -13.66% =========================================== Files 70 269 +199 Lines 1715 6846 +5131 =========================================== + Hits 1405 4674 +3269 - Misses 310 2172 +1862 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.