feat(generic): Reintroducing the generic SQL module (#892)

Related to #884
Trying to replace the old generic.py in core to a nicer version under
the generic module.

`SqlContainer` its not as good (in being generic) as `ServerContainer`
but it should allow us to deprecate
`core/testcontainers/core/generic.py` with minimal effort for users, it
could lead to a more Generic version like `DBContainer` in the future.

Update 1: Refactor to use `SqlConnectWaitStrategy`
Update 2: Now `SqlConnectWaitStrategy` is required and the users can
provide `SqlContainer` with any wait strategy.
Update 3: Now utilizes all the latest improvements from `WaitStrategy`

Note: I think the added tests + documentation (provided in this PR) are
by themselves a great improvement over the current generic.py