fix: AfterQuery using safer right trim while clearing from clause's j…

[bhowmik-abhijeet]

Summary:
As a fix to #7025 , clearing of db.Statement.Clauses["FROM"] was in introduced in #7027

At https://github.com/go-gorm/gorm/blob/master/callbacks/query.go#L291 , it can cause a panic if db.Statement.Clauses["FROM"].Joins slice is being sliced using negative upper bound index
i.e. when len(db.Statement.Joins) > len(v.Joins). Please observe below the case reproduced in current source code

Steps to reproduce:

In the case above, wrong column name pets.names (instead of pets.name) is passed as query.
When Count() is called after Find() on the the same gorm.DB instance with a wrong query, it calls AfterQuery twice which in turn tries to trim the slice twice which now is empty after first trim. Hence instead of obtaining actual SQL error, it causes a panic due to index out of bound error.

Checklist:

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?:
This Pull Request:
Safely trims the db.Statement.Clauses["FROM"].Joins
Unit test for newly added functions for Safe right trimming of slice

User Case:
In one of my our projects, we are using gorm (just fantastic) as ORM support for Postgres. After upgrading gorm version from v1.9.16 -> v1.25.11, we identified panic in API due to broken migration which changes a column name causing the query to be wrong.

Of course this is a minor fix requirement but much needed to prevent API server error and handle SQL error gracefully.

[bhowmik-abhijeet]

@liov Could you please kindly review and provide further suggestions? Thanks.