Change default interpretation of real literals from DOUBLE to DECIMAL

[mxwli]

In principle should fix #3949 Breaks a million other tests because decimal -> string formatting is slightly different from double -> string formatting, leading to errors where tests expect 1.000000 but get 1.0. This is probably not the only cause but it's very prevalent Uses inferMinimalType from the csv-sniffing branch to determine whether or not the string should be interpreted as a decimal or double.

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