feat: add rounding logic and scale zero fix fro parse_decimal to match parse_string_to_decimal_native behavior

[himadripal]

Which issue does this PR close?

Which issue does this PR close?

• Related to DataFusion should support casting strings such as "4e7" to decimal datafusion#10315
• Follows up - Fix: Support for e notation using existing parse_decimal in string to decimal conversion #6905 ,based on the (Fix: Support for e notation using existing parse_decimal in string to decimal conversion #6905 (comment))

Few important consideration -

• Existing string to decimal conversion uses parse_string_to_decimal_native
• parse_string_to_decimal_native does not have support for e-notation
• parse_string_to_decimal_native does rounding at scale, not truncate
• parse_decimal an existing method has e-notation support and use elsewhere
• Fix: Support for e notation using existing parse_decimal in string to decimal conversion #6905 added rounding support in parse_decimal
• moved string to decimal conversion to use parse_decimal to get support for e-notation.

This PR is a 2nd one to break up #6905 , this one add rounding logic to parse_decimal to match the behavior in existing parse_string_to_decimal_native.

Closes #.

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?