Refactor: some "trivial" changes

[Root-Core]

I've extracted some code from #203 that doesn't have much to do with pathlib stuff.
Most of the changes are "less than trivial" and the gamefixes are more or less unchanged.

Changes to gamefixes:

• 508980
  • Changed string concatenation to use of pathlib
• 2475980 (Gobliiins 5)
  • reimplemented, tested and extended to handle the demo version (2505910)
• 294700 / 497360
  • moved the dos-device creation to util.py
  • no functional change
• 22330
  • moved class Redirect to util.py as class ReplaceType
  • type will be reused in later patches
  • no functional change
• 497360
  • Reduced nesting
  • no functional change
• 39500 / 65600
  • Unified
  • Removed unnecessary path join
  • no functional change

[Root-Core]

Some quick debugging:

The CI error does not seem to be related to the PR.
We call get_valid_appids() several times and at one point the server (or the python Steam client) returns this:

{'meta_data_only': True, 'response_pending': False, 'http_min_size': 1024, 'http_host': 'clientconfig.akamai.steamstatic.com'}

Which obviously doesn't contain the key apps. So we should check if apps exists or handle the error somehow.
More research needed.