[clang-tidy] Cache the locations of NOLINTBEGIN/END blocks

Support for NOLINT(BEGIN/END) blocks (implemented in D108560) is
currently costly. This patch aims to improve the performance with the
following changes:

- The use of tokenized NOLINTs instead of a series of repetitive ad-hoc
string operations (`find()`, `split()`, `slice()`, regex matching etc).
- The caching of NOLINT(BEGIN/END) block locations. Determining these
locations each time a new diagnostic is raised is wasteful as it
requires reading and parsing the entire source file.

Move NOLINT-specific code from `ClangTidyDiagnosticConsumer` to new
purpose-built class `NoLintDirectiveHandler`.

Differential Revision: https://reviews.llvm.org/D116085