Remove Docker provider

[Amulyam24]

Docker provider has been deprecated and this PR aims to remove it.

Note: dependent on #3071 to be merged

[mkulke]

@Amulyam24 can you rebase this PR?

[Amulyam24]

@Amulyam24 can you rebase this PR?

Hi @mkulke, rebased the PR, PTAL, Thanks!

[wainersm]

Hi @Amulyam24 , thanks for raising this PR! Just for general awareness, @stevenhorsman is working to get the release 0.21 done but the removal of the docker provider is planned only for 0.22.

[mkulke]

@Amulyam24 headsup: I rebased the PR via github, it still has a "hold" tag. so, we want to wait for the release to go through. but the tests should in theory start to turn green now.

[mkulke]

another rebase required and the mkosi Makefiles still seem to reference some docker files, see failed e2e tests. we can use "git grep docker" to find references.

[stevenhorsman]

LGTM. Unfortunately do to the badly timed merge you will need to resolve the conflict, but after that this is good to go. Thanks for the update!

[mkulke]

@copilot resolve the merge conflicts in this pull request

[mkulke]

oh, copilot can't fix problems on forks (lucklily)

[Amulyam24]

Rebased the PR, PTAL!