Support env variables based on ConfigMaps sent in payload

[jakub-dzon]

What this PR does / why we need it:

This PR adds support for providing ConfigMap YAML definitions as part of podman play kube input. ConfigMap provided this way can be referred to as a source of environments variables for pods.

So far it has only been possible to use ConfigMaps defined in files local to podman starting the pods using --configmaps parameter, which does not work in remote scenarios (even if the HTTP call is made withing the same host).
This PR aims at dealing with the same problem as the other attempt in #12243.

How to verify it

Add ConfigMap definition to a YAML multidoc and refer to it in a container defined in a pod in the same file; properties defined in the ConfigMap will be visible in the pod as environment variables. See https://github.com/containers/podman/pull/12371/files#diff-cef3dd63f572aaef036dce65d94140edbfa8c350c2fc836e864a6b1ef653db87R2952 or https://github.com/containers/podman/pull/12371/files#diff-cef3dd63f572aaef036dce65d94140edbfa8c350c2fc836e864a6b1ef653db87R3022

Which issue(s) this PR fixes:

Fixes #12363

[rhatdan]

@umohnani8 PTAL

[rhatdan]

Thanks @jakub-dzon But tests are not happy.

[jakub-dzon]

Looks like some env issue:

# cd .; git clone -- https://go.googlesource.com/tools /var/tmp/go/src/golang.org/x/tools
Cloning into '/var/tmp/go/src/golang.org/x/tools'...
error: 14768 bytes of body are still expected
fetch-pack: unexpected disconnect while reading sideband packet
fatal: early EOF
fatal: fetch-pack: invalid index-pack output
package golang.org/x/tools/cmd/goimports: exit status 128

Rebasing.

[rhatdan]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jakub-dzon, rhatdan

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [rhatdan]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[umohnani8]

LGTM

[jakub-dzon]

One questions, otherwise LGTM

Thank you!

[rhatdan]

/lgtm

[jakub-dzon]

@rhatdan: would you agree to backporting this feature to the 3.x line so we can consume it sooner than v4 would be released?
There are no breaking changes introduced by this PR and it should be fairly simple to backport.

[rhatdan]

Sure open a Back port PR and we can get it merged and into the next bugfix release.

[jakub-dzon]

Sure open a Back port PR and we can get it merged and into the next bugfix release.

Thank you! I've created #12447.