cmake: cleanup Findgperftools.cmake

cmake: cleanup Findgperftools.cmake

* remove Findtcmalloc.cmake, use Findgperftools.cmake instead.
* tcmalloc is packaged in gperftools-dev, so we can check them in a single
  place.
* fix the check of heap-profiler.h, we should enable the check as long
  as tcmalloc is enabled or profiler is enabled.
* only check gperftools headers in "include/gperftools", and do not
  "include/google" anymore. as we only support the distros which
  shipping recent gperftools-dev package with "include/gperftools".
  and "google/*.h" are deprecated.
* set ALLOC_LIBS with GPERFTOOLS_TCMALLOC_LIBRARY, so we can link
  against tcmalloc with full path.

Signed-off-by: Kefu Chai <kchai@redhat.com>