feat: run initializations before starting main process

[reubenmiller]

Proposed changes

Run tedge init using root user to setup the service before starting the main process. This allows folders to be created on startup rather than during installation time (see linked ticket for further details).

Notes

• + is only used on services where the main process is run under a non-root user, e.g. tedge - see systemd.service docs
• - is used when running the tedge init so that any initialization failure does not block attempting to start the main process (to avoid errors in non critical actions run in tedge init from blocking the starting of the main process)
• support for systemd versions < 231 is dropped with this PR, though the linux distributions that use systemd < 231 are either EOL or about to be EOL (within 6 months)

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

#2448

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

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
367	0	3	367	100	54m43.494999999s