Remove RealT conversion from SVector

[huiyuxie]

The inner type conversion is too dynamic for GPU kernels and it caused errors in my place during kernel compilation. But if the type conversion is removed, the kernel compilation looks good.

But it will bring some Float64 computation - do you @ranocha think it is Ok?

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.34%. Comparing base (480aea9) to head (9cb33a6).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2099   +/-   ##
=======================================
  Coverage   96.34%   96.34%           
=======================================
  Files         470      470           
  Lines       37497    37503    +6     
=======================================
+ Hits        36125    36131    +6     
  Misses       1372     1372           

Flag	Coverage Δ
unittests	96.34% <100.00%> (+<0.01%)	⬆️

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[ranocha]

But it will bring some Float64 computation

If there is a reasonable way to avoid Float64, I would prefer that

[huiyuxie]

I cannot understand why we have to avoid Float64 entirely - GPU has tolerance for mixed precision.

[huiyuxie]

Please do not merge - I don't think it is a good way.