Lenient doctor

[RuRo]

Description

qmk doctor is a bit too strict on a couple of issues, which can lead to false-positive warnings:

1. To determine if the qmk_firmware home is a git repository, the doctor checks, if ${QMK_FIRMWARE}/.git is a directory. However, if qmk_firmware is a git submodule, then .git will be a file instead of a directory. This PR relaxes the requirement, allowing .git to be a file.

2. When checking for the installed udev rules, the doctor searches only in /etc/udev/rules.d/*.rules. According to man udev, this isn't the only directory, where udev rules can be located:

   RULES FILES
          The udev rules are read from the files located in the system rules directories /usr/lib/udev/rules.d
          and /usr/local/lib/udev/rules.d, the volatile runtime directory /run/udev/rules.d and the local
          administration directory /etc/udev/rules.d.
   

   In particular, the official arch/manjaro qmk package places the udev rules into /usr/lib/udev/rules.d/50-qmk.rules, leading to a false positive. This PR makes the doctor also search for udev rules in /usr/lib/udev/rules.d/, /usr/local/lib/udev/rules.d/ and /run/udev/rules.d/.

Types of Changes

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

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).