Update CMake to formally name the five levels of ABACUS executables (Useful Information for knowing Five Compilation Levels of ABACUS)

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Update CMake to formally name the five levels of ABACUS executables.

ABACUS Compilation Guide: From Basic to Advanced

1. Basic Concepts of Compilation
Compilation is the process of converting source code into executable files, which mainly includes the following steps:
Preprocessing – handles macro definitions and header file inclusions
Compilation – converts source code into assembly code
Assembly – converts assembly code into machine code
Linking – links multiple object files into an executable file
For large-scale scientific computing software such as ABACUS, the compilation process is more complex and requires handling various dependencies and configuration options.

2. Five Compilation Levels of ABACUS
ABACUS provides five compilation levels, from basic to advanced, to meet different computing requirements.

Level 1: pw (Plane-Wave)
This level uses only the plane-wave basis set and disables the linear combination of atomic orbitals (LCAO). It is suitable for simple plane-wave calculations with fast speed and relatively low memory usage.

Level 2: basic
This level enables LCAO and provides basic quantum chemistry calculation functions. It is designed for fundamental electronic structure calculations of molecules and solids.

Level 3: std (Standard)
Based on the Basic level, this level adds support for LibRI libraries for hybrid functional calculations. It is suitable for accurate electronic structure calculations and spectral simulations.

Level 4: ml (Machine Learning)
Based on the Basic level, this level integrates machine learning algorithms. It is used for large-scale material screening and property prediction accelerated by machine learning.

Level 5: max
This is the full-featured version that integrates all functions of the Std and ML levels, with testing enabled. It is intended for development and debugging of new features.

3. Naming Rules of Compilation Scripts
Numbers 1–5 represent the five compilation levels (PW, Basic, Std, ML, MAX).
Letters indicate parallelism and function types:

ser: serial version
para: parallel version
gpu: GPU version

4. Core Dependencies
Core Dependencies
FFTW3 for fast Fourier transform
BLAS / LAPACK for linear algebra operations
ScaLAPACK for parallel linear algebra
MPI for parallel computing
OpenMP for multi-threading
LibXC for exchange-correlation functionals
Advanced Dependencies
ELPA for eigenvalue solvers in LCAO
Cereal for serialization
LibRI and LibComm for hybrid functionals (Std, MAX)
LibTorch and libnpy for machine learning (ML, MAX)
CUDA for GPU acceleration

5. Version Selection
PW: Low hardware requirements; simple electronic structure calculations.
Basic: Medium requirements; standard LCAO calculations.
Std: Medium–high requirements; hybrid functional calculations.
ML: High requirements; machine learning–accelerated computations.
MAX: High requirements; full features for development and testing.

6. Compilation Workflow
Install dependencies (compiler, CMake, math libraries, etc.).
Create a build directory and run CMake with corresponding options.
Compile with make -j.
Install with make install.

7. Summary
ABACUS uses a five-level compilation system (PW, Basic, Std, ML, MAX) to support flexible configurations from basic to full functions. Correct compilation settings ensure computational efficiency and accuracy for materials simulation and scientific research.