fixing fast float stod conversion according to ST_Number schema specification

[gangatp]

• Allowing leading + sign

• Not allowing , separated values

  • example: for a comma separated value 123,456 . The result from from_chars will be result=123.0 and answer.ptr = ',456'

  auto answer = fast_float::from_chars(input.data(), input.data()+input.size(), result); if(answer.ec != std::errc()) { // check error } if(answer.ptr[0] == ',') { // unexpected delimiter }

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (e77162c) 69.19% compared to head (324ed58) 69.20%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #339 +/- ## ======================================== Coverage 69.19% 69.20% ======================================== Files 271 271 Lines 28688 28691 +3 ======================================== + Hits 19851 19855 +4 + Misses 8837 8836 -1 ```

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