Config overhaul: improve admin experience

[josecelano]

• Add a warning when the configuration does not enable any service (UDP tracker, HTTP tracker, or tracker API). It does not make sense to run the app without services enabled.
• Write the final used config to the logs when the tracker starts. We are only writing the config values when the source is an env var. We should do it always and print out the final configuration after merging sources (defaults -> TOML file -> env vars).

[josecelano]

This is how it looks now when you run the tracker:

[josecelano]

ACK 397ef0f6d003d4887272b6e25a2c5bbad9cc96c8

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 6.66667% with 14 lines in your changes missing coverage. Please review.

Project coverage is 77.41%. Comparing base (de8ed61) to head (397ef0f).

Files	Patch %	Lines
src/app.rs	0.00%	4 Missing :warning:
packages/configuration/src/v2/mod.rs	0.00%	3 Missing :warning:
packages/configuration/src/lib.rs	33.33%	2 Missing :warning:
src/bootstrap/app.rs	0.00%	1 Missing :warning:
src/bootstrap/logging.rs	0.00%	1 Missing :warning:
src/console/ci/e2e/runner.rs	0.00%	1 Missing :warning:
src/console/clients/checker/app.rs	0.00%	1 Missing :warning:
src/console/clients/udp/app.rs	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #941 +/- ## =========================================== - Coverage 77.47% 77.41% -0.07% =========================================== Files 183 183 Lines 9666 9674 +8 =========================================== Hits 7489 7489 - Misses 2177 2185 +8 ```

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