[clang-tidy] readability-simplify-boolean-expr detects negated literals

Adds support for detecting cases like `if (!true) ...`.
Addresses [[ https://bugs.llvm.org/show_bug.cgi?id=47166 | readability-simplify-boolean-expr not detected for negated boolean literals. ]]

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D86176