Move the installer into the core

[m-vo]

This PR moves the Installer into the core bundle and removes the ability to run migrations from the install tool.

With this change, also both the sqlCompileCommands hook as well as the parsing and grouping of SQL commands is removed. The order and command grouping now matches the output of doctrine's schema diff (which finally solves #2792 (comment)).

The first commit (1406bc3) is only about moving things around without changing the implementation - to get a better idea about the actual code changes, you might want to base your diff view on this commit.

/cc @ausi

[aschempp]

Two questions:

1. any particular reason we're not just moving the existing classes to the core-bundle and keep everything as is, since I assume we want to get rid of all this stuff anyway?
2. any reason to remove stuff from the installation bundle? I mean shouldn't we just remove the installation-bundle from contao/contao in one PR?

[ausi]

since I assume we want to get rid of all this stuff anyway?

Don’t think so, this stuff is all needed, isn’t it?

[m-vo]

any reason to remove stuff from the installation bundle?

The install bundle will not work anymore without the removed command grouping logic.

[m-vo]

I readded the ability to distinguish between all schema updates + those that remove columns in b12d4ab. We're now effectively copying the columns that should be remove to the $toSchema which makes them disappear in the diff.

[ausi]

❤️

[leofeyer]

Thank you @m-vo.