Add an explicit toggle for the static analyzer in clang-tidy

Instead of using CLANG_ENABLE_STATIC_ANALYZER for use of the
static analyzer in both clang and clang-tidy, add a second
toggle CLANG_TIDY_ENABLE_STATIC_ANALYZER.

This allows enabling the static analyzer in clang-tidy while
disabling it in clang.

Differential Revison: https://reviews.llvm.org/D87118