[FEA] Optimize JSON reading of floating-point values

[andygrove]

Is your feature request related to a problem? Please describe.
PR #4825 fixes some edge cases with parsing JSON numeric types but introduces an additional complex regular expression and also calls into GpuCast.sanitizeStringToFloat which also executes a complex regular expression which is mostly redundant for this path.

Describe the solution you'd like
The JSON reader should implement optimized custom code for casting string to float instead of re-using the GpuCast logic.

Describe alternatives you've considered
None

Additional context
None