feat: create an internal sdk for docker contexts and docker configs

[mdelapenya]

• feat: create a seed for an sdk in the internal package
• chore: wrap errors
• chore: use new dockerconfig package instead of cpuguy83's
• chore: run mod tidy

What does this PR do?

This PR adds two packages into a new internal docker package:

• context: locates and loads docker contexts from the docker config path.
• config: locates and reads docker config from the docker config path.

The config package embedes the cpuyguy83's dockercfg package, to have control on the config and auth types.

Why is it important?

Both new packages could represent the seed for an eventual docker-sdk-go package, that would naturally emerge from this internal set of packages.

They are internal in order to iterate faster, and not break clients of testcontainers-go.

Related issues

• #2810 would benefit from this new context package, so it must be updated to use it instead.

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[mdelapenya]

@stevenh I think this PR would be the foundation for the internal SDK in which the work for the new docker client could land.

Can we prioritise this PR if possible?