[io] Better support for logging in fibers

[salkinium]

IOStream would not yield when BlockIfFull behavior was used (the default for all our boards). But yielding when full would create interlaced output from different fibers, so I implemented a mutex that only unlocks on newlines. So all fibers will wait until one entire line has been produced, then yield. So this now only blocks fibers that wait on the logger output, and not all fibers in the system. The change is backward compatible for when not using fibers.

Other changes:

• Prevent a circular header dependency due to IOStream being referenced everywhere.
• std::scoped_lock is not enabled in the stdlibc++ for GCC14. Dunno why, but couldn't fix it in any way.
• Tested in Hardware
• Documentation