[clang] NFCI: Optimize storage and lookup of analyzer options

This patch moves `llvm::sort()` from `AnalyzerOptions` constructor to initialization of local static variable in `isUnknownAnalyzerConfig()`.

This avoids unnecessary work, which can speed up Clang tools that initialize lots of `CompilerInvocation`s (and therefore `AnalyzerOptions`).

Reviewed By: steakhal

Differential Revision: https://reviews.llvm.org/D137258