CLI: Udev related fixes and improvements

[Erovia]

Description

• Only check ModemManager if Caterina udev rule is not found.

• Not all udev implementations support 'RUN{builtin}+="uaccess"', so we only check it on systemd systems where systemd-udevd is likely used.

@sigprof could you test it with eudev?

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[sigprof]

I'm not sure that using RUN{builtin}+="uaccess" directly was actually intended by systemd developers. A related bug report asking for some documentation for the uaccess mechanism (systemd/systemd#4288) is unanswered since 2016, but it seems that the intended usage is to use just TAG+="uaccess" in rules (which must come before 73-seat-late.rules), and rely on the appropriate utility (either the uaccess builtin, or elogind-uaccess-command as used in elogind/elogind#47) to be called from 73-seat-late.rules. Also in theory the support for the uaccess builtin is optional even in the real udev from systemd (the rule which calls it from 73-seat-late.rules is guarded by the HAVE_ACL compile time condition).

As for ModemManager, it could be running even without systemd (at least Void Linux has the corresponding package, but I don't have any hardware which actually needs it), therefore removing the warning completely for such systems might not be 100% correct.

[Erovia]

Yes, RUN{builtin}+="uaccess" shouldn't be needed in theory, but for some reason it was in practice.
Anyway, I'm open to improving the rules, so I'll do some testing again.

ModemManager: This PR does not remove any functionality, as we currently only test MM if systemctl is present. I realize this is a shortcoming and MM can run with other inits, that's why I added the TODO to implement the checks for other service managers.

[Erovia]

After doing some testing with the help of D3vastat0r and Dasky from Discord, the RUN{builtin}+="uaccess" seems to be unnecessary.
So I removed them from the udev file and from the checks as well.

Also, doctor's state handling is more complicated as it's now has 3 states:

• everything a-ok
• minor stuffs were found, e.g.: missing udev rules
• major stuffs were found, e.g.: missing tools

The output should be more informative, especially for new-comers.
I hope it will be clearer if something is just a warning.