BUG #18976: -0.0 with float8 will be transformed to 0 in prepare statement but not in normal execution

The following bug has been logged on the website:

Bug reference:      18976
Logged by:          Chi Zhang
Email address:      798604270@qq.com
PostgreSQL version: 18beta1
Operating system:   Ubuntu 24.04 and docker
Description:        

The value -0.0 with float8 is transformed to 0 in prepared statements but
remains -0 in normal execution. Although 0 and -0 are numerically equal,
this discrepancy can lead to subtle bugs in certain cases—for example, when
the value is cast to a VARCHAR, as illustrated below.
```
PREPARE prepare_query (float8) AS SELECT CAST($1 AS VARCHAR) =
CAST(-0.0::float8 AS VARCHAR);
EXECUTE prepare_query(-0.0); -- f
```