[slimtensor] Add common_shims_slim with basic property getters

[Gasoonjia]

Stack from ghstack (oldest at bottom):

• [slimtensor] Add from_etensor factory function for ETensor to SlimTensor conversion #16551
• rename slimtensor fiies to consistent with executorch files #16469
• [slimtensor] Add utility functions to common_shims_slim #16457
• [slimtensor] Add storage and device property getters to common_shims_slim #16455
• -> [slimtensor] Add common_shims_slim with basic property getters #16454

Add SlimTensor-based implementations of basic property getter AOTI shim functions:

1. aoti_torch_get_data_ptr() - Returns pointer to tensor data
2. aoti_torch_get_sizes() - Returns pointer to sizes array (SlimTensor stores int64_t directly)
3. aoti_torch_get_strides() - Returns pointer to strides array (SlimTensor stores int64_t directly)
4. aoti_torch_get_dtype() - Returns the scalar type as int32_t
5. aoti_torch_get_dim() - Returns the number of dimensions

Key design:

• Create a new common_shim_slim.h for working on new API while not impact the current pipeline. Will use common_shim_slim.{h/cpp} to replace current common_shim.{h/cpp} when everything has been set up.
• Uses #ifdef CUDA_AVAILABLE conditional compilation to seperate the implementation between cuda backend and mps backend since SlimTensor hasn't have mps support yet. Will remove the branch once SlimTensor support mps.
• Refactored to a header-only library so the caller's preprocessor flags determine which tensor type is used. This design supports both CUDA backend (SlimTensor) and MPS backend (ETensor) from a single library.

Differential Revision: D90126254

[pytorch-bot]

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❌ 1 New Failure, 1 Pending, 2 Unrelated Failures

As of commit 3d9e562 with merge base 99348ed ():

NEW FAILURE - The following job has failed:

• Test CUDA Builds / test-model-cuda-e2e (mistralai, Voxtral-Mini-3B-2507, quantized-int4-tile-packed) / linux-job (gh)
  RuntimeError: Command docker exec -t f632b2db0e9eda3671316bdc945fae5cc23a6fdfc7bcb9f6ace20288cc58becf /exec failed with exit code 1

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• Test Metal Backend / test-model-metal-e2e (openai, whisper-small, non-quantized) / macos-job (gh) (similar failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

BROKEN TRUNK - The following job failed but was present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• Test Metal Backend / test-model-metal-e2e (openai, whisper-large-v3-turbo, non-quantized) / macos-job (gh) (trunk failure)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

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