[clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

The original check did break the green buildbot in the sanitizer build.
It took a while to redroduce and understand the issue.

There occured a stackoverflow while parsing the AST. The testcase with
256 case labels was the problem because each case label added another
stackframe. It seemed that the issue occured only in 'RelWithDebInfo' builds
and not in normal sanitizer builds.

To simplify the matchers the recognition for the different kinds of switch
statements has been moved into a seperate function and will not be done with
ASTMatchers. This is an attempt to reduce recursion and stacksize as well.

The new check removed this big testcase. Covering all possible values is still
implemented for bitfields and works there. The same logic on integer types
will lead to the issue.

Running it over LLVM gives the following results:


Differential: https://reviews.llvm.org/D40737
llvm-svn: 328107