Reland "[memprof] Extend the index prof format to include memory profiles."

This reverts commit 0f73fb18.

Use llvm/Profile/MIBEntryDef.inc instead of relative path.

Generated the raw profile data with `-mllvm
-enable-name-compression=false` so that builbots where the reader is
built without zlib do not fail.

Also updated the test build instructions.