Fix sqlx-cli create, drop, migrate

[cycraig]

Description

Fix the db create, db drop, and migrate run commands for sqlx-cli. Edit: this is for the latest changes on main for 0.7.

Fixes the following errors running those commands:

thread 'main' panicked at 'No drivers installed. Please see the documentation in sqlx::any for details.', sqlx-core/src/any/driver.rs:143:33

and

error: while executing migrations: error with configuration: SQLite driver does not support migrations or migrate feature was not enabled

Changes

• Uncomment default and database features for sqlx-cli.
• Install database drivers in sqlx-cli.
• Implement AnyConnectionBackend::as_migrate for databases.

How to test or review this PR

• Checkout this branch and install sqlx-cli.

cargo install -f --path ./sqlx-cli

• Use the SQLite example.

cd examples/sqlite/todos
export DATABASE_URL="sqlite:${PWD}/todos.db"

• Create the DB and run migrations, they should succeed with no errors.

sqlx db create
sqlx migrate run

• Don't forget to reinstall the released sqlx-cli 0.6 version locally.

cargo install -f sqlx-cli

[abonander]

Oh, this must mean we don't have any functionality tests for sqlx-cli, should probably fix that at some point.