feat: refactored tracker db folder structure. added alembic migrations

[MiNeves00]

LLMstudio Version X.X.X

What was done in this PR:

• Large Refactor of llmstudio_tracker/db file organization into folders per type instead of per table.
• Added alembic migrations for schema migrations
• Added integration test for checking that writing to tracker db is working

How it was tested:

• Integration & Unit Tests
• Tested migrations for sqlite & postgres DB

Additional notes:

• added alembic as a dependency