Add Statement Batching For PtOnlineSchemaChangeConnection

[Watercycle]

Overview

See #26. This PR makes it so that every individual statement generated as part of ZeroDowntimeSchema::table gets passed along to pt-online-schema-change in one go, which is both more performant and seemingly in-line with how native Schema-based migrations work.

Thoughts

1. I plan to battle test this a little more; but, was curious if anyone has any initial concerns with this approach? (which was originally laid out by @dbhynds in the linked issue)
2. If we're concerned about overriding Blueprint, perhaps we could make it an opt-in feature by adding in a Laravel version check, a zero-downtime.php + ['batched' => true] config option, and/or a static variable would de-risk the change? The most immediate concern that comes to mind is that this will be incompatible with other libraries overriding Blueprint.

Testing

I haven't extensively manually tested this change yet; but, as a smoke-test, it works with several of my company's migrations and has been batching groups of $table->dropForeign and $table->foreign calls correctly.

[Daursu]

Thanks for submitting this PR. I do like the approach, and I'm good with overriding the Blueprint class when importing this package, as we are actually falling back onto the original behavior when using a connection that doesn't support batching.

I'll try to setup a GitHub workflow that automatically tests the package against all supported versions of Laravel & PHP versions to ensure we are not introducing any breaking changes.

[Watercycle]

The test matrix is the most sure-fire way; but, I think this should be PHP 7.0 compatible and Laravel 5 (src) compatible, now.

[Daursu]

I've added integration tests against both Percona and gh-ost on the main branch. I think we need to rebase your PR against it to force the tests to run. I also dropped support for older versions of PHP and Laravel in future releases, as they are no longer maintained.

[Watercycle]

Awesome! I'll give this another pass in the coming days.

[Watercycle]

Thank you for taking the time to bump the dependencies and expand the tests! It looks like the tests passed on my fork. Is there anything else you'd like me to follow-up with?

[Daursu]

Looks good to me. I'll merge it in and will create a new release for it

[Daursu]

Thank you for contributing, this was on the TODO list for a while 😄