feat(core): Private registry

[Tranquility2]

Ref #562

This enhancement adds capability to utilize the env var DOCKER_AUTH_CONFIG in-order to login to a private docker registry.

[alexanderankin]

i wonder if this is what the java client does underneath, have almost no opportunity to find out independently. i explored the testcontainers side of java yesterday and realized that i need to look at docker-java to find any real answers anyways.

[Tranquility2]

Added tests

[Tranquility2]

Some documentation on how I tested it: https://gist.github.com/Tranquility2/20652b77a012ee54ae1c8ca021aea1ff

[alexanderankin]

wdyt about testing using this module - https://github.com/testcontainers/testcontainers-python/tree/main/modules/registry - i know it inverts the dependencies on their head a bit. maybe we can just copy and paste the code as it is just a part of the test suite and therefore not actually being published to pypi. doesn't have to be a part of this PR, just think that would be the most comprehensive/on-brand test.

maybe its not actually a blocker, just pausing to think cause when this is merged, there is no more fixes for 4.4 line (RP will set the version in #551 to 4.5.x)

[Tranquility2]

was thinking the same thing :) I had the exact same doubt as its not really a best practice but fits like a glove for a more comprehensive test. Do you think it should be in this PR or another? In any case I'll be happy to add it.