Add support for PostgreSQL version() in SQL federation

[somiljain2006]

Fixes #37436

Changes proposed in this pull request:

• Add support for PostgreSQL version() function in SQL federation
• Register version function in pg_catalog via PostgreSQLSQLFederationFunctionRegister
• Implement version() in the PostgreSQL federation function layer
• Add unit tests to verify function registration and behavior
• Ensure no registration occurs outside the pg_catalog schema

How was this tested?

1. Verified using the provided Docker Compose setup with ShardingSphere Proxy
2. Enabled SQL federation and connected via psql
3. Executed select version();
4. Confirmed query no longer throws SQL federation error
5. Verified correct version string is returned

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• I have added corresponding unit tests for my changes.
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[somiljain2006]

@terrymanu @menghaoranss @taojintianxia @RaigorJiang @strongduanmu @FlyingZC Can you please review this pr?

[strongduanmu]

Hi @somiljain2006, can you add e2e test in db_tbl_sql_federation scenario?

[somiljain2006]

I think there is some problem with my logic, as after running the e2e test, it shows errors so therefore im marking this pr as draft till i came up with my new logic