MB-63430: Add jemalloc option

[CascadingRadium]

• Add support for a new CMake option to enable FAISS to use the jemalloc memory allocator.
• Setting -DFAISS_USE_JEMALLOC=ON during the Faiss build enables this feature
  (disabled by default).
• Jemalloc is detected in the build system either via pkg-config or by specifying
  -DJemalloc_Root=<path> as a CMake option. The <path> must point to a
  JemallocConfig.cmake file.
• Jemalloc must be built with the je_ prefix; otherwise, the build will fail.
• When this feature is enabled, the faiss_c and faiss libraries will be linked to the
  jemalloc library.