Extend CSV schema inference to allow scientific notation for floating point types

[pjmore]

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@matthewmturner is working on adding datafusion to the h2oai database benchmarks. Some of the csv data uses scientific notation which the current schema inference does not support. apache/datafusion#1488

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Extend floating point schema inference to recognize numbers in valid scientific notation. This only requires updating the DECIMAL_RE regex that is used during schema inference as lexical_core already supports parsing numbers in this form.

Describe alternatives you've considered
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Implementing alternative csv schema inference in datafusion.