[ET-VK][ez] Fix vulkan_schema interface and link Vulkan to pybindings

[SS-JIA]

Summary:

Changes

First, small update to vulkan_schema interface in the CMakeLists.txt, which fixes a build error like:

  CMake Error in backends/vulkan/CMakeLists.txt:
    Target "vulkan_schema" INTERFACE_INCLUDE_DIRECTORIES property contains
    path:

      "/pytorch/executorch/pip-out/temp.linux-x86_64-cpython-310/cmake-out/schema/include"

    which is prefixed in the build directory.

Then, make the pybindings link against to the vulkan backend if it is built. This allows model testing through Python via _load_for_executorch_from_buffer.

Test Plan:
CI

cc @manuelcandales @cbilgin

[SS-JIA]

Stack from ghstack (oldest at bottom):

• [DNL] small change to trigger CI testing #13300
• [ET-VK][CI] Add vulkan CI to test exporting and running models #13295
• [ET-VK][examples] Create export script for Vulkan examples #13294
• -> [ET-VK][ez] Fix vulkan_schema interface and link Vulkan to pybindings #13327
• [ET-VK] Add optional blocklist and allowlist to vulkan partitioner to aid debugging #13326

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/13327

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❌ 1 New Failure, 1 Pending

As of commit 5730a1d with merge base 71c9a4f ():

NEW FAILURE - The following job has failed:

• Build documentation / build (buck2) / Build doc (gh)

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