Refine Mod CPU implement

[jysh1214]

The Cytnx arithmetic implementation contained lots duplicated code across different type combinations, which caused:

• Difficult maintenance when updating logic
• Low code readability due to repetitive patterns

This PR refines the Mod CPU implementation, similar to https://github.com/Cytnx-dev/Cytnx/pull/651. Our goal is to generalize all arithmetic operations using templates, and eventually refactor the multiple-dispatch mechanism for arithmetic.

template <typename TLin, typename TRin>
void ArithmeticInternalImpl(...) {
  if (type == 0)
    cytnx::linalg_internal::AddInternalImpl<TLin, TRin>(
      out, Lin, Rin, len, shape, invmapper_L, invmapper_R);
  else if (type == 1)
    cytnx::linalg_internal::MulInternalImpl<TLin, TRin>(
      out, Lin, Rin, len, shape, invmapper_L, invmapper_R);
  else if (type == 2)
    // ...
  else
    // ...
}

Next, we plan to replace the linalg_internal::lii.Ari_ii usage in arithmetic .cpp files with the std::variant + std::visit pattern, similar to what we did in commit 710c98c.

I will refine src/backend/linalg_internal_cpu/Arithmetic_internal.cpp in next PR.

[codecov[bot]]

Codecov Report

:x: Patch coverage is 3.68852% with 235 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 31.99%. Comparing base (cc12e63) to head (4d95705). :warning: Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
...ackend/linalg_internal_cpu/Arithmetic_internal.cpp	0.96%	205 Missing :warning:
src/backend/linalg_internal_cpu/Mod_internal.hpp	18.91%	28 Missing and 2 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #704      +/-   ##
==========================================
+ Coverage   30.19%   31.99%   +1.79%     
==========================================
  Files         215      215              
  Lines       38332    36192    -2140     
  Branches    15471    14520     -951     
==========================================
+ Hits        11576    11578       +2     
+ Misses      24855    22713    -2142     
  Partials     1901     1901              

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[jysh1214]

Hi @IvanaGyro, We can pass CI now. Could you take a look? Thx.