Additions
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- Symmetry operations as contextmanager (see examples ewf/molecules/73 and ewf/molecules/74)
- Inversion and reflection symmetry
- Direct contraction of ERI blocks with 2-DM cumulant blocks for RCCSD,
  without building complete cluster 2-DM cumulant.
- Support for two DMET-cluster projectors in MP2-BNO construction
- EwDMET (energy-weighted DMET) bath orbitals
- CISD initial guess for CCSD solver

Fixes
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- MPI SCF decorator for molecules with density-fitting
- Wrong shape bug in UMP2-BNO construction in large systems
- Wrong shape bug for rotational symmetry for basis sets with
  multiple l>0 shells per PySCF bas index