feat(orm): implement dependencies for migrations

[m4tx]

For now the system only really create dependency on the previous migration in the app. Eventually we'll extend this to handle ForeignKeys and other relationship types as well.

[codecov]

Codecov Report

Attention: Patch coverage is 94.11765% with 27 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
flareon/src/db/migrations/sorter.rs	96.36%	12 Missing ⚠️
flareon-cli/src/migration_generator.rs	84.05%	11 Missing ⚠️
flareon/src/db/migrations.rs	90.90%	3 Missing ⚠️
flareon/src/lib.rs	0.00%	1 Missing ⚠️

Flag	Coverage Δ
rust	83.99% <94.11%> (+0.80%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
flareon/src/db.rs	91.32% <ø> (ø)
flareon/src/test.rs	95.65% <100.00%> (+0.53%)	⬆️
flareon/src/lib.rs	57.57% <0.00%> (ø)
flareon/src/db/migrations.rs	85.82% <90.90%> (+0.14%)	⬆️
flareon-cli/src/migration_generator.rs	71.02% <84.05%> (+1.88%)	⬆️
flareon/src/db/migrations/sorter.rs	96.36% <96.36%> (ø)

[seqre]

LGTM