Integrate hashtree for better hashing performance (#5188)

status-im/nim-ssz-serialization#35 brings in https://github.com/prysmaticlabs/hashtree as a supported backend for SHA256, giving a nice little performance boost to all hash_tree_root calls on supported platforms / compilers.

Expected gains are on the order of 30% which in the case of a replayed state nets us 0.2-0.3s improvement.

More about this design here: https://hackmd.io/@potuz/BJyrx9DOF - kudos to @potuz for this excellent library!

.github/workflows/ci.yml

@@ -138,6 +138,10 @@ jobs:
             fi
           fi
 
+          if [[ '${{ runner.os }}' == 'Windows' ]]; then
+            export NIMFLAGS="${NIMFLAGS} --cc:clang"
+          fi
+
           export NIMFLAGS="${NIMFLAGS} ${{ matrix.nimflags-extra }}"
           echo "NIMFLAGS=${NIMFLAGS}" >> $GITHUB_ENV
 
@@ -178,7 +182,7 @@ jobs:
 
       - name: Build binaries (with trace logging enabled)
         run: |
-          ${make_cmd} -j ${ncpu} V=1 NIM_COMMIT=${{ matrix.branch }} LOG_LEVEL=TRACE NIMFLAGS="-u:release --opt:none ${{ matrix.nimflags-extra }}"
+          ${make_cmd} -j ${ncpu} V=1 NIM_COMMIT=${{ matrix.branch }} LOG_LEVEL=TRACE NIMFLAGS="-u:release --opt:none ${NIMFLAGS}"
           # The Windows image runs out of disk space, so make some room
           rm -rf build nimcache