misc: Extend cast tests in the expression fuzzer

[rui-mo]

This PR enables tests for from-decimal and to-decimal conversions in the Presto and Spark expression fuzzer. Tests for cast(real/double as timestamp) is enabled for Spark expression fuzzer. Two issues on the cast(varchar as decimal) were fixed:

1. Returns error status when the exponent part is empty.
2. Status::UserError internally uses fmt::vformat which throws below exception when the string contains placeholder { or }. This PR removes the details from error message.

   uncaught exception of type fmt::v10::format_error: unmatched '}' in format string

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