Add nvc and nvc++ as supported C/C++ compilers

[robertmaynard]

Currently based on #1889 to get the refactoring of the compiler detection needed to support nvc, and nvc++.

The nvhpc compiler suite has implicit force includes which effects the pre-processor output as seen below:

root@6c8ec2a4e037:~# cat test.cpp 
root@6c8ec2a4e037:~# nvc -E test.cpp 
# 1 "test.cpp"
# 1 "/opt/nvidia/hpc_sdk/Linux_x86_64/23.7/compilers/include/_cplus_macros.h" 1 3
# 1 "test.cpp" 2
# 1 "/opt/nvidia/hpc_sdk/Linux_x86_64/23.7/compilers/include/_cplus_preinclude.h" 1 3
 

struct __va_list_tag {
  unsigned int gp_offset;
  unsigned int fp_offset;
  char *overflow_arg_area;
  char *reg_save_area;
};

# 27 "/opt/nvidia/hpc_sdk/Linux_x86_64/23.7/compilers/include/_cplus_preinclude.h" 3

typedef struct __va_list_tag __pgi_va_list[1];

# 41 "/opt/nvidia/hpc_sdk/Linux_x86_64/23.7/compilers/include/_cplus_preinclude.h" 3

# 1 "test.cpp" 2

[codecov-commenter]

Codecov Report

Attention: 107 lines in your changes are missing coverage. Please review.

Comparison is base (8253364) 29.77% compared to head (006c3fc) 29.78%.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #1891    +/-   ##
========================================
  Coverage   29.77%   29.78%            
========================================
  Files          49       50     +1     
  Lines       17699    17857   +158     
  Branches     8524     8603    +79     
========================================
+ Hits         5270     5318    +48     
- Misses       7311     7383    +72     
- Partials     5118     5156    +38     

Files	Coverage Δ
tests/system.rs	26.16% <0.00%> (ø)
src/compiler/c.rs	37.99% <0.00%> (-0.65%)	⬇️
src/compiler/compiler.rs	36.41% <33.33%> (-0.12%)	⬇️
src/compiler/nvhpc.rs	34.09% <34.09%> (ø)

... and 10 files with indirect coverage changes

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[sylvestre]

as expected, it needs some conflicts fixes

[robertmaynard]

as expected, it needs some conflicts fixes

Rebased on latest main