[1.x] Extract insert all

[timacdonald]

This PR extracts an insertMany method to make extending the database driver easier.

Some of the community (https://github.com/laravel/pennant/pull/104#issuecomment-2135085391, https://github.com/laravel/pennant/issues/100) are extending the driver to add custom fields to the features table. With the recent changes unique constraint handling (https://github.com/laravel/pennant/pull/104) we introduced a new insert query that is not able to be intercepted in an extended class.

This PR extracts the query out to an insertMany method to make it easier to intercept and decorate.

Additionally it:

• Makes the existing insert method a proxy to the new insertMany method.
• Fixes a minor typo in the exception message.
• Adds some tests for the unique constraint handling.