MbedTLS changed a lot of internals with their LTS version 3.6.0, which
are incompatible with the find module currently shipped with
OBS Studio.
The solution requires several changes to be applied at once:
* Rename the generated target name to MbedTLS::mbedtls to match the
name used by MbedTLS' own CMake package
* Update find module to use the updated target name(s)
* Set CMAKE_FIND_PACKAGE_PREFER_CONFIG to TRUE before trying to find
MbedTLS to ensure that CMake package files are used with priority
(Those are shipped only with MbedTLS 3.6.0 in obs-deps).
* A deprecation warning is emitted if the find module is used with
MbedTLS 3.6.0 available
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