refactor(core): Standardize configuration and readiness steps in container lifecycle

[santi]

Aims for this PR:

• Include _configure() and _wait_until_ready() hooks in base DockerContainer image to be used by all container implementations in need of a configuration and readiness step.
• Standardize method naming for getting a connection string from a container, where a popular client library expects a standardized URL format for connecting to the service provided by the container (E.g. a database URL for DB containers)
• Remove DbContainer class, as the two points above will render it redundant.

[santi]

Referencing https://github.com/testcontainers/testcontainers-python/issues/459 for context

[alexanderankin]

would this have the potential to break existing code that depends on conventions from v3 and v4?

[alexanderankin]

if i were to try to merge this, what should i keep in mind @santi ? Anything not already reflected here? I did a first pass and seems like i will have to revisit this several times in order to make sense of this fully...

also, like i asked above, is this breaking at all?

[santi]

@alexanderankin Hey, sorry for the delay on this one. This is just a WIP draft that is not ready for a merge quite yet, and has probably drifted a bit from the main branch. I intend on getting this one up-to-date this week, and do a nice write-up on the implications and document the intention behind the changes / API standardisation it introduces.