[11.x] Fix modifying auto-increment columns

[hafezdivandari]

This PR fixes handling auto-increment columns on some edge cases:

Create a compound primary with an auto-increment column

All databases except SQLite support creating a table with a compound/composite primary key with an auto-increment column:

Schema::create('test', function (Blueprint $table) {
    $table->bigIncrements('id');
    $table->uuid('uuid');

    $table->primary(['id', 'uuid']);
});

Modifying an auto-increment column

All databases except SQL Server support modifying an auto-increment/primary column:

// Create
Schema::create('test', function (Blueprint $table) {
    $table->increments('id');
});

// Change
Schema::table('test', function (Blueprint $table) {
    $table->bigIncrements('id')->change();
});

Changing a column to auto-increment

MySQL, MariaDB and SQLite support changing a regular column to an auto-increment column, but you must explicitly include primary modifier for this to work:

// Create
Schema::create('test', function (Blueprint $table) {
    $table->unsignedBigInteger('id');
});

// Change
Schema::table('test', function (Blueprint $table) {
    $table->bigIncrements('id')->primary()->change();
});

Upgrade Guide

We should add a note to docs:

The change method does not change indexes of a column. Therefore, you may use index modifiers explicitly to add/drop an index when modifying the column:

$table->bigIncrements('id')->primary()->change();
$table->char('postal_code', 10)->unique(false)->change();

[github-actions]

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[taylorotwell]

@hafezdivandari can you PR the upgrade guide? Thanks