[Tests] Skip source-tree-only tests in wheel testing

[tlopex]

This pr skip tests that require a source checkout when running against the Python wheel.

The apache-tvm==0.25.0rc0 wheel does not include the source/include tree needed by tvm.libinfo.find_include_path(). Some tests call export_library() or JIT through the C host backend, which then fails in wheel testing with:

AssertionError: Cannot find the source directory given ffi_dir: .../site-packages/tvm

[gemini-code-assist]

Code Review

This pull request updates several test files in the codegen and relax test suites to skip specific tests during wheel testing. This is achieved by adding the @tvm.testing.skip_if_wheel_test decorator to individual test functions and parameterizing the 'c' target with the skip mark. There are no review comments, and I have no feedback to provide.

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