Remove pkg.yml and adjust versioning logic

[nanory]

What this PR does / why we need it:
This PR gets rid of the pkg.yml and ensures that the Git Tag of a project determines the version of the package. Otherwise, the Git commit hash is taken

Which issue(s) this PR fixes:
Fixes #5

[gardener-robot]

@nanory Thank you for your contribution.

[alee-ntap]

Tested this workflow changes works with apt_source, git_source and also native three different type of packages:
https://github.com/gardenlinux/package-htop/actions/runs/6983646731
https://github.com/gardenlinux/package-iproute2/actions/runs/7003594089
https://github.com/gardenlinux/package-iproute2/actions/runs/7004046530

I think we may now drop the hardcoded ref: feature/5-remove-pkg-yml and merge.

[alee-ntap]

I'm now dropping the hardcoded ref: feature/5-remove-pkg-yml line. Ready for merge,.

[alee-ntap]

I started to migrate package-systemd, and I found we can optimize the build.yml by use:

jobs:
  build_pkg:
    uses: gardenlinux/package-build/.github/workflows/build_pkg.yml@main

So that we don’t need --arg name "$name" '.jobs[$name]. in the yq command in build_source script.
So that all thebuild.yml files from other package-* will be only has difference on the first line with name, eg:

name: systemd

I will adjust the workflow in this PR.