fix(cc): remove C++ 17 usage (deepmodeling#4570)

Fix deepmodeling#4569.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Build Configuration**
- Enhanced flexibility in C++ standard settings based on project
dependencies
	- Added conditional checks for setting C++ standard version

- **Code Improvements**
	- Updated type checking mechanisms in compute methods
- Refined method signatures for handling different data types in
DeepPotPT and DeepSpinPT classes

- **Technical Refinements**
	- Improved conditional compilation and configuration handling
	- Introduced more flexible type-specific method overloads

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: njzjz

source/CMakeLists.txt

@@ -15,7 +15,9 @@ set(DEEPMD_C_ROOT
     ""
     CACHE PATH "Path to imported DeePMD-kit C library")
 
-set(CMAKE_CXX_STANDARD 11)
+if(NOT DEFINED CMAKE_CXX_STANDARD)
+  set(CMAKE_CXX_STANDARD 11)
+endif()
 macro(set_if_higher VARIABLE VALUE)
   # ${VARIABLE} is a variable name, not a string
   if(${VARIABLE} LESS "${VALUE}")

source/api_cc/src/DeepPotPT.cc

@@ -143,7 +143,7 @@ void DeepPotPT::compute(ENERGYVTYPE& ener,
   int natoms = atype.size();
   auto options = torch::TensorOptions().dtype(torch::kFloat64);
   torch::ScalarType floatType = torch::kFloat64;
-  if (std::is_same_v<VALUETYPE, float>) {
+  if (std::is_same<VALUETYPE, float>::value) {
     options = torch::TensorOptions().dtype(torch::kFloat32);
     floatType = torch::kFloat32;
   }
@@ -341,7 +341,7 @@ void DeepPotPT::compute(ENERGYVTYPE& ener,
   int natoms = atype.size();
   auto options = torch::TensorOptions().dtype(torch::kFloat64);
   torch::ScalarType floatType = torch::kFloat64;
-  if (std::is_same_v<VALUETYPE, float>) {
+  if (std::is_same<VALUETYPE, float>::value) {
     options = torch::TensorOptions().dtype(torch::kFloat32);
     floatType = torch::kFloat32;
   }

source/api_cc/src/DeepSpinPT.cc

@@ -145,7 +145,7 @@ void DeepSpinPT::compute(ENERGYVTYPE& ener,
   int natoms = atype.size();
   auto options = torch::TensorOptions().dtype(torch::kFloat64);
   torch::ScalarType floatType = torch::kFloat64;
-  if (std::is_same_v<VALUETYPE, float>) {
+  if (std::is_same<VALUETYPE, float>::value) {
     options = torch::TensorOptions().dtype(torch::kFloat32);
     floatType = torch::kFloat32;
   }
@@ -365,7 +365,7 @@ void DeepSpinPT::compute(ENERGYVTYPE& ener,
   int natoms = atype.size();
   auto options = torch::TensorOptions().dtype(torch::kFloat64);
   torch::ScalarType floatType = torch::kFloat64;
-  if (std::is_same_v<VALUETYPE, float>) {
+  if (std::is_same<VALUETYPE, float>::value) {
     options = torch::TensorOptions().dtype(torch::kFloat32);
     floatType = torch::kFloat32;
   }