delete libpaw （useless)

[mohanchen]

delete libpaw （useless)

[Cstandardlib]

LGTM!
Please also note that there are still some paw-related leftovers in the codebase and documentation, such as:

python/pyabacus/src/hsolver/py_hsolver.cpp
148:            use_paw : bool
157:        "use_paw"_a,

python/pyabacus/src/hsolver/py_diago_david.hpp
109:        bool use_paw,
146:            use_paw,

python/pyabacus/src/hsolver/diago_adapter.hpp
87:        bool use_paw,
98:            use_paw,

python/pyabacus/src/pyabacus/hsolver/_hsolver.py
139:    use_paw: bool = False,
166:    use_paw : bool, optional
198:        use_paw,

python/pyabacus/src/ModuleESolver/interfaces/i_diagonalizer.hpp
61:    bool use_paw = false;        ///< Use PAW method

python/pyabacus/src/ModuleESolver/components/diagonalizer_wrapper.hpp
159:            config_.use_paw,

source/source_hsolver/diago_david.cpp
19:                                  const bool use_paw_in,
21:    : nband(nband_in), dim(dim_in), nbase_x(david_ndim_in * nband_in), david_ndim(david_ndim_in), use_paw(use_paw_in), diag_comm(diag_comm_in)

source/source_hsolver/test/hsolver_pw_sup.h
126:                                  const bool use_paw_in,
128:    : nband(nband_in), dim(dim_in), nbase_x(david_ndim_in * nband_in), david_ndim(david_ndim_in), use_paw(use_paw_in), diag_comm(diag_comm_in) {

source/source_hsolver/hsolver_pw_sdft.h
23:                   const bool use_paw_in,
34:                               use_paw_in,

source/source_hsolver/hsolver_pw.cpp
113:            this->paw_func_in_kloop(ik, tpiba);
137:            this->call_paw_cell_set_currentk(ik);
160:            this->paw_func_in_kloop(ik, tpiba);
179:            this->call_paw_cell_set_currentk(ik);
353:        DiagoDavid<T, Device> david(pre_condition.data(), nband, dim, PARAM.inp.pw_diag_ndim, this->use_paw, comm_info);

source/source_hsolver/diago_david.h
48:     * @param[in] use_paw_in Flag indicating whether to use PAW.
60:               const bool use_paw_in,
145:    bool use_paw = false;

source/source_pw/module_pwdft/forces.cpp
52:    ModuleBase::matrix forcepaw(nat, 3);

source/source_hsolver/hsolver_pw.h
31:              const bool use_paw_in,
40:          use_paw(use_paw_in), use_uspp(use_uspp_in), nspin(nspin_in), scf_iter(scf_iter_in),
79:    const bool use_paw;
104:    void paw_func_in_kloop(const int ik,
107:    void call_paw_cell_set_currentk(const int ik);
109:    void paw_func_after_kloop(psi::Psi<T, Device>& psi, elecstate::ElecState* pes,const double tpiba,const int nat);

cmake/FindMKL.cmake
115:# For compatibility with legacy libpaw_interface CMakeLists.txt

docs/CONTRIBUTING.md
56:|   |-- module_paw              The module for performing PAW calculations.

docs/advanced/pp_orb.md
130:- [THEOS](http://theossrv1.epfl.ch/Main/Pseudopotentials): PSlibrary 0.3.1, a library of pseudopotentials for DFT calculations, including ultrasoft, paw, norm-conserving both full-relativistic and scalar-relativistic pseudopotentials.

[mohanchen]

That's helpful suggestions. Thanks.