Schema validations to match Java

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• I searched in the issues and found nothing similar.

Description

Add missing schema validations in SchemaBuilder::build() to match Java's Schema.normalizeColumns():

• reject duplicate PK columns
• require auto-increment columns to be INT/BIGINT and not part of the primary key
• require a primary key when auto-increment is used
• reject empty/whitespace column names and constraint names
• etc that makes sense in the current state

Willingness to contribute

• I'm willing to submit a PR!