feat(experimental): Shuffle packages and tidy up

[mfridman]

This PR is mechanical and basic cleanups, with one fix for out-of-order migrations.

It adds a lot more tests to the core implementation. Once satisfies we'll move this into the top-level goose package, and also expose the global SetGlobalGoMigrations and ResetGlobalGoMigrations.

┌─────────────────────────────────────────────────────────────────────────────────────────────────┐
│  STATUS │ ELAPSED │                    PACKAGE                    │ COVER │ PASS │ FAIL │ SKIP  │
│─────────┼─────────┼───────────────────────────────────────────────┼───────┼──────┼──────┼───────│
│  PASS   │  1.79s  │ github.com/pressly/goose/v3/internal/provider │ 82.7% │  60  │  0   │  1    │
└─────────────────────────────────────────────────────────────────────────────────────────────────┘

[mfridman]

Remove this. Instead, we calculate this based on the functions.

I think a limitation with the old system is the inability to set an up (with tx) and a down (without a tx). We should be able to support different up / down combinations.