Separate OS and architecture in integration tests

[hohwille]

Task summary

See (resolved) review discussion in PR #1657

 local osType
  case "$OSTYPE" in
    msys*|cygwin*|win32*)
      osType="windows-x64"

This is actually wrong. I tested this on Windows@ARM64 and it gives me windows-x64.
However, the architecture does not seem to matter in any of our integration tests.
IMHO this is somehow coming from the replaced MATRIX_OS.
I would suggest that we simply remove the architecture since the method names are only about the operating system: doGetOsType, doIsWindows, doIsMacOs.
If we later need a separation by architecture, we can add another function for that.

Additional context

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