[SYCL] Extract sycl-post-link utilities to SYCLPostLink library (#21678)
Move file I/O and module processing utilities from sycl-post-link tool
to new Utils.h/cpp. Extracts saveModuleIR, saveModuleProperties,
saveModuleSymbolTable, and isTargetCompatibleWithModule functions.
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Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>