[SYCL][NFC] Refactor FunctionCategorizer to simple functions. (#17529)

During a code review of the Module Splitting upstreaming patch, it was
recognized that the FunctionCategorizer is overengineered. This change
removes the FunctionCategorizer and replaces it with plain functions.
The rules "SimpleFlagAttribute," "SimpleFlagMetadata," and
"SortedIntegersListMetadata" haven't been used and are therefore
abandoned.

The aim of this change is to simplify the future upstreaming of Module
Splitting.

Author: maksimsab