Remove core/clang/versions.mk and scan-build wrapper

* Use the definitions of ClangDefaultBase and ClangDefaultVersion
  in build/soong/cc/config/global.go.
* scan-build is too old;
  replaced by better clang-tidy's -clang-analyzer-* checks.
* WITH_STATIC_ANALYZER is still effective
  to invoke ccc-analyzer or c++-analyzer.

Test: make checkbuild
Change-Id: Ifd159dd28e529d5d3c9807f5e391911365da8cdb