Workaround for Adam.step's lazy initialization of its inner state

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#### The next comment explains what this issue aims at

When `thunder.jit` trace `optimizer._init_group` before this initialization, calls of the jitted `optimizer.step` will all reset the inner state. To make it work correctly, the following conditions are necessary:
* The obtained trace does not initialize the inner state.
* The inner state gets initialized independently from trace execution.

To get consistent `optimizer.state_dict()` requires another condition:
* The actual tensors (not their proxies) are accessible on initialization.

The simplest way would be to actually call `optimizer._init_group` at the early stage to guarantee the inner state is initialized before tracing it.

Start with thunder.jit tracing around optimizer._init_group and optimizer.step, then inspect how optimizer.state_dict() observes the inner state. The work is done when tracing no longer resets that state and state_dict() exposes the actual initialized tensors rather than proxies.

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