NIFI-15601 Improved the TIME_DURATION_REGEX in DurationFormat.java to accurately capture a positive decimal number with or without a leading integer.

[dan-s1]

Summary

NIFI-15601
In order to standardize the exceptions thrown, I improved the TIME_DURATION_REGEX regular expression in DurationFormat to capture a positive decimal number whether it has a leading integer or not and not allow for more than one period.
In addition to adding unit tests to test when the duration value has illegal characters, I also added another case to an existing parameterized test testGetPreciseTimeDurationWithDecimalNumbers to test a decimal that does not even have a leading zero.

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