Remove python-gil requirement and enable free-threaded Python

[ndgrigorian]

This PR removes the required python-gil dependency from the dpctl conda package workflow and enables free-threaded Python in extension modules

Adjustments are made to the SequentialOrderManager class such that the class is safe in free-threaded, including mutexes in the C++ class as a fall-back in case of (not recommended) simultaneous access to its members and methods

Caching using defaultdict such as that in SequentialOrderManager and the queue and device managers are also adjusted to be more thread-safe, using lazily initialized factory functions so each thread will carry its own cache or manager

This PR builds on top of work already done removing the tensor submodule, which is pending migration to dpnp

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