Enable macros to use certain things from the OS module when the target OS is not supported

[PMunch]

Essentially this PR removes the {.error.} pragmas littered around in the OS module and submodules which prevents them from being imported if the target OS is not supported. This made it impossible to use certain supported features of the OS module in macros from a supported host OS. Instead of the {.error.} pragmas the oscommon module now has a constant supportedSystem which is false in the cases where the {.error.} pragmas where generated. All procedures which can't be run by macros is also not declared when supportedSystem is false.

It would be possible to create dummy versions of the omitted functions with an {.error.} pragma that would trigger upon their use, but this is currently not done.

This properly fixes #19414

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Thanks for your hard work on this PR!
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