[PATCH] Normalize numeric/bigint scientific notation after rounding

Hi hackers,

While working with PG, I found that to_char returns value that is
right but the format is wrong:
SELECT to_char(999::numeric, '9.9EEEE');
Result is: 10.0e+02, and I think the expected output should be: 1.0e+03.
With help from ChatGPT, I figured that get_str_from_var_sci()
determines the exponent
before rounding the significand. If rounding increases the
significand's absolute value to
10, the original exponent is still used. The attached patch adds a
check for this,and adjusts
the significand and the exponent.

Regards,
hanjianqiao