[SYCL] Fix bindless image sample instruction generation (#21345)
The SPIR-V specification requires the result type of the
`OpImageSampleExplicitLod` instruction to be a vector of four
components. The SYCL bindless images extension allows the user to
specify a return type for the `sample_image` call that may not be a
vector. This commit ensures the SYCL headers correctly convert between
the user-specified type and the type required by the SPIR-V
specification to prevent generating invalid SPIR-V modules.
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Signed-off-by: Michael Aziz <michael.aziz@intel.com>
