fix(MySQL): keep auto-increment columns out of the primary key

[roxblnfk]

🔍 What was changed

• integer() / bigInteger() with autoIncrement: true no longer end up in the primary key on MySQL: setPrimaryKeys(['id']) stays ['id'], and the column keeps its declared abstract type.
• Reflecting an existing table returns its real primary key; an AUTO_INCREMENT column outside it is reported as integer / bigInteger, so saving the same declaration again produces no diff.
• Indexes on an AUTO_INCREMENT column that does not lead the primary key are written into CREATE TABLE, since MySQL rejects such a column without a key (error 1075). A column that is in neither the primary key nor an index now fails with a SchemaException naming it.
• smallPrimary() now works on MySQL: it used to be created without the primary key and failed with 1075.

Review notes

• MySQL columns now carry an internal isPrimary flag, the same model Postgres uses for serial; only primary-key columns reverse-map to primary / smallPrimary / bigPrimary. The flag is excluded from column comparison: primary key changes are already compared at the table level.
• Adding an AUTO_INCREMENT column to an existing table still creates its index after ALTER TABLE … ADD COLUMN and fails the same way. That path is unchanged here.

Checklist

• Fixes [Bug]: MySQL autoIncrement column is always added to the primary key #274
• How was this tested:
  • Functional tests added (MySQL, live server)
  • Full suites run locally: MySQL 8.0, PostgreSQL 15, SQL Server 2019, SQLite, Unit

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.71%. Comparing base (75fb8f2) to head (d6eea82).

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x     #275      +/-   ##
============================================
+ Coverage     95.61%   95.71%   +0.10%     
- Complexity     2230     2242      +12     
============================================
  Files           142      142              
  Lines          6341     6374      +33     
============================================
+ Hits           6063     6101      +38     
+ Misses          278      273       -5     

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