Merge #4410

4410: Implement the experimental log mode cli flag and log level updates at runtime r=dureuill a=irevoire

# Pull Request
This PR fixes two issues at once because they’re highly correlated in the codebase.

## Related issue
Fixes https://github.com/meilisearch/meilisearch/issues/4415
Fixes https://github.com/meilisearch/meilisearch/issues/4413

## What does this PR do?
- It makes the fmt logger configurable to output json or human-readable logs (like we already do today)
- It moves the fmt logger under a `reload` layer so we can update its targets at runtime
- Add the possibility to stream logs in the json mode
- Adds an analytics for the new CLI flag

Co-authored-by: Tamo <tamo@meilisearch.com>

meilisearch/Cargo.toml

@@ -104,7 +104,7 @@ serde_urlencoded = "0.7.1"
 termcolor = "1.4.1"
 url = { version = "2.5.0", features = ["serde"] }
 tracing = "0.1.40"
-tracing-subscriber = "0.3.18"
+tracing-subscriber = { version = "0.3.18", features = ["json"] }
 tracing-trace = { version = "0.1.0", path = "../tracing-trace" }
 tracing-actix-web = "0.7.9"