Refactor not_empty_string macro to fix alias bugs and catch invisible…

[shivasingh4945-tech]

What changed & why:

• No more syntax crashes: The old code tried to alias the column (as {{ column_name }}), which broke dbt if we tested a nested column (like user.email) or a SQL function. I moved the logic straight into the WHERE clause so it works on everything.
• Catches sneaky characters: Standard trim() was missing invisible characters like tabs and newlines. This now catches those so completely blank strings actually fail the test like they are supposed to.
• Faster queries: Instead of doing 4 separate string scans with nested replace() functions, it now uses translate() to swap out all hidden characters in one fast pass.

Tested and verified on normal text, empty strings, spaces, tabs, and NULLs!

[shivasingh4945-tech]

Hi @remigabillet @mjumbewu @haf @zqureshi
I have tested this fix on PostgreSQL and it works correctly.

Would love your feedback on this approach.
Happy to make any changes needed!