[Refactor] Make @tensorclass work properly with pyright

[Mxbonn]

Description

Describe your changes in detail.

Motivation and Context

@tensorclass() # works without typing issues
class MyClass:
    a = torch.Tensor
    b = torch.Tensor
    
@tensorclass # results in pyright typing issues and is arguably more commonly used than @tensorclass() with parentheses
class MyClass:
    a = torch.Tensor
    b = torch.Tensor

pyright: error:

Argument of type "type[MyClass]" cannot be assigned to parameter "autocast" of type "bool" in function "__new__"
  "type[type]" is not assignable to "type[bool]"Pylance[reportArgumentType](https://github.com/microsoft/pyright/blob/main/docs/configuration.md#reportArgumentType)

Types of changes

I looked at the @dataclass implementation and mimicked the behavior here. I'm no expert in typing.

• typing change

Potential breaking change:
Technically you could have used @tensordict the following:
@tensordict(<bool_for_autocast_without_using_the_keyword>)
or
@tensordict(<bool_for_autocast_without_using_the_keyword>, <bool_for_frozen_without_using_the_keyword>)

This will break now but I doubt any sane person uses it like that, cs.github.com did not show any such usage when I looked for it.

Checklist

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