[sqllogictest] Consolidate normalization code for the postgres and non-postgres paths

[alamb]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
#4834 adds a way to run sqllogictests using postgres 🦾 (kudos to @melgenek )

However, it uses different normalization code for the postgres and non-postgres paths

Describe the solution you'd like

I would like a single set of comparison code that works for both postgres and not postgres paths

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
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