Feature: Symmetry=1 for EXX

[maki49]

fix #2881

Step 1

Now EXX calculation can also use symmetry to reduce k-points! I've tested a few cases: examples/hse/lcao_Si2 and tests/integrate/81x_NO_LT_${brav}, the results seem to be reasonable. Welcome to try and meet bugs : -)

Thanks to @minyez for his note.

Step 2

Using symmetry to reduce atom pairs and lattice in real space (done, can be merged after the loop3 branch of LibRI is merged)