Fix: plugins don't update their internal representation of config files on file change

[Ruadhri17]

Proposed changes

Fix the problem of not updating the internal representation of config files. This applies to all plugins that use FsFileWatcher:

• tedge-log-plugin
• c8y-log-plugin
• c8y-configuration-plugin

Additionally this PR fixes unsafe unwrap while sending mqtt message inside the c8y-configuration-plugin (that could lead to rust panic if there was any problem with MQTT actor)

The integration tests were also extended to cover these scenarios to ensure it functions as expected (taken from #2260):

• add library function to check service status of child devices and switch to new tedge interface
• use recent timestamp instead of 1970 as this is more aligned to how the UI behaves
• fix timestamp bug where the tests were using a fixed timezone which meant that the local time was being erroneously cast to UTC leading to unexpected dateFrom/dateTo values
• use tedge config to control te topic instead of flags
• add notes about when workarounds in tests can be removed

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

• tedge-log-plugin does not detect file changes to tedge-log-plugin.toml #2246

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

Merging #2262 (8e1b1c6) into main (07d88c2) will increase coverage by 0.0%.
The diff coverage is 63.6%.

Additional details and impacted files

Files Changed	Coverage Δ
crates/extensions/c8y_config_manager/src/actor.rs	58.7% <33.3%> (+0.5%)	⬆️
crates/extensions/c8y_log_manager/src/actor.rs	75.9% <75.0%> (-0.3%)	⬇️
crates/extensions/tedge_log_manager/src/actor.rs	68.9% <75.0%> (-0.8%)	⬇️

... and 4 files with indirect coverage changes

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
273	0	5	273	100	51m5.924999999s

[reubenmiller]

@Ruadhri17 I merged the changes from #2260 as the integration tests were covering this aspect, so we can get confirmation that everything works as expected before merging (I also rebased ontop of the latest from main)

[albinsuresh]

The fix looks good. Happy to approve once my queries are addressed.