Split base factory helpers

[vmoens]

Summary

• move tensordict.base factory helpers into tensordict._base.factories
• keep tensordict.base as the compatibility facade for the moved helpers
• add tests that lock legacy import paths and public __module__ values

BC notes

• existing imports from tensordict, tensordict.base, tensordict._td, tensordict._lazy, tensordict.tensorclass, and tensordict.store._store remain valid
• moved factory helpers keep __module__ == "tensordict.base"

Test plan

• python -m pytest test/test_compatibility.py::test_legacy_import_paths_are_preserved test/test_compatibility.py::test_public_class_modules_are_preserved -q
• python -m pytest test/test_tensordict.py -k "from_dict or from_namedtuple or from_struct_array or from_tuple or from_csv or from_json or from_parquet or from_pandas" -q
• python -m pytest test/test_compatibility.py -q -k "not redis and not StoreFromSchema and not Preallocation"
• python -m compileall -q tensordict/_base tensordict/base.py

Full test/test_compatibility.py is not runnable in my local environment because Redis Python support is installed but no Redis server is listening on localhost:6379.

[github-actions]

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[BugFix] or [Fix]	bug	[BugFix] Fix memory leak in TensorDict
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[Refactor]	Refactor	[Refactor] Clean up module imports
[CI]	CI	[CI] Fix workflow permissions
[Test] or [Tests]	Test	[Test] Add unit tests for nn module
[Compile]	Compile	[Compile] Fix torch.compile issue
[Performance] or [Perf]	Performance	[Perf] Optimize tensor operations
[Deprecation]	Deprecation	[Deprecation] Mark old function
[Setup]	setup	[Setup] Update build configuration
[Distributed] or [Dist]	Distributed	[Distributed] Add scatter collective
[Benchmark] or [Bench]	Benchmarks	[Benchmark] Add compile benchmark
[Typing] or [Type]	Typing	[Typing] Add type stubs
[BC-breaking] or [BC]	BC-breaking	[BC-breaking] Remove deprecated API
[Formatting] or [Format]	Formatting	[Format] Fix code style
[Quality]	Quality	[Quality] Improve error messages

Note: Matching is case-insensitive. Common variations (singular/plural) are supported.

[github-actions]

PR Title Label Error

PR title must start with a label prefix in brackets (e.g., [BugFix]).

Current title: Split base factory helpers

Supported Prefixes

Your PR title must start with exactly one of these prefixes (case-insensitive):

Prefix	Label Applied	Example
[BugFix] or [Fix]	bug	[BugFix] Fix memory leak in TensorDict
[Feature]	Feature	[Feature] Add new storage backend
[Doc] or [Docs]	documentation	[Doc] Update installation guide
[Refactor]	Refactor	[Refactor] Clean up module imports
[CI]	CI	[CI] Fix workflow permissions
[Test] or [Tests]	Test	[Test] Add unit tests for nn module
[Compile]	Compile	[Compile] Fix torch.compile issue
[Performance] or [Perf]	Performance	[Perf] Optimize tensor operations
[Deprecation]	Deprecation	[Deprecation] Mark old function
[Setup]	setup	[Setup] Update build configuration
[Distributed] or [Dist]	Distributed	[Distributed] Add scatter collective
[Benchmark] or [Bench]	Benchmarks	[Benchmark] Add compile benchmark
[Typing] or [Type]	Typing	[Typing] Add type stubs
[BC-breaking] or [BC]	BC-breaking	[BC-breaking] Remove deprecated API
[Formatting] or [Format]	Formatting	[Format] Fix code style
[Quality]	Quality	[Quality] Improve error messages

Note: Matching is case-insensitive. Common variations (singular/plural) are supported.