Separate docker images and containers data to different files/folders

**Is your feature request related to a problem? Please describe.**
For now all docker data are stored into `%USERPROFILE%\AppData\Local\Docker\wsl\data\ext4.vhdx`. File `ext4.vhdx` can become very large due too many images or too many container runs. The last one is very important during development when I need to build a new container every time.

From other side (and as I understand) images/layers are very infrequent data and are stored in gz archives. So they can be stored in HDD - here we save space and lifetime for SSD.

**Describe the solution you'd like**
Add the ability to separate docker images and docker container stores. I can store large image data on HDD and use SSD for containers (or event mount RAM for them)

Start by investigating how Docker data is stored in %USERPROFILE%\AppData\Local\Docker\wsl\data\ext4.vhdx and how WSL exposes that storage. No source files or tests are named, so first identify the relevant storage configuration and integration points. Done means image data and container data can be assigned to separate user-selectable locations.

Written by the indexing model from the issue text.