BugFix: M1 detection

[SSE4]

closes: #8499
continues story in #8113
it turns out the function _detect_os_arch (part of the detect_defaults_settings) didn't use detected_architecture and used its own mapping.
I guess it's better to have changes unified, done within a single place, so it's harder to forget to update both functions (like in the case of M1).

another confusing thing was:

ERROR: Your ARM 'arm64' architecture is probably not defined in settings.yml
Please check your conan.conf and settings.yml files

which emitted the error event after arm64 was added to the settings.yml. I also corrected that, so the function always loads the settings. (to be honest, I am not even sure the error message is needed at all, as it doesn't play nice with custom settings).

Changelog: BugFix: Fix Apple M1 detection.
Docs: omit

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[jgsogo]

Nice addition and refactor!