tracing: Add --trace-json for visualising traces and add more spans

[Bravo555]

TODO

• remove some too verbose events
• adjust span levels

Proposed changes

Add --trace-json option that when used causes a trace-TIMESTAMP.json file will be created which can be opened by tools like https://ui.perfetto.dev.

Also added more spans, particularly on the Actor::run method, so that we can easily see which actor emitted new span/event.

Example: Before new spans

trace-1736783287825075.json

Example: After new spans

trace-1736784244896393.json

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s)
• I ran cargo fmt as mentioned in CODING_GUIDELINES
• I used cargo clippy as mentioned in CODING_GUIDELINES
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

[codecov]

Codecov Report

❌ Patch coverage is 87.06897% with 15 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...mon/tedge_config/src/system_services/log_config.rs	79.54%	8 Missing and 1 partial ⚠️
crates/core/tedge_actors/src/channels.rs	80.00%	0 Missing and 2 partials ⚠️
crates/common/tedge_config/src/cli.rs	0.00%	1 Missing ⚠️
crates/core/tedge_actors/src/message_boxes.rs	66.66%	0 Missing and 1 partial ⚠️
crates/core/tedge_mapper/src/c8y/mapper.rs	0.00%	1 Missing ⚠️
crates/core/tedge_mapper/src/lib.rs	0.00%	1 Missing ⚠️

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[didier-wenzek]

This PR would deserve some clean-up to focus on its main ideas (better use of tracing spans and trace visualization using tracing-chrome).

I agree that tracing span is a powerful tool to improve thin-edge debug-ability. However, I need more evidence to be convinced by visual traces.
I think efforts need to be made elsewhere first, on what is traced and on the level of details.