[Code]: Migrate docker containers to Alpine Linux

[mikekazakov]

Task Type

Migration

Description

Right now there are three docker containers used for integration tests.
They use a regular full Ubuntu image, which takes quite some time to set up and start up, especially on GH runners.
Ideally Alpine should be used instead to shave off a few minutes from the integration runtime.

Additional Information

The integration tests implicitly rely on the directory structure of the system they connect to, so they need to be updated correspondingly as well.
Dockerfiles are located here: https://github.com/mikekazakov/nimble-commander/tree/main/Source/VFS/tests/data/docker