CMP discovery doesn't get the ARGOCD_* env

[farcaller]

Checklist:

• I've searched in the docs and FAQ for my answer: https://bit.ly/argocd-faq.
• I've included steps to reproduce the bug.
• I've pasted the output of argocd version.

Describe the bug

Forked from #13940. The plugin discovery via executing a command should get the same environment as the actual plugin execution to have the detailed context.

It'd be nice to also update the docs to explicitly state that the environment is passed through.

To Reproduce

Run env >&2; exit 1 as the discover.find.command.

Expected behavior

The env prints all the ARGOCD_* variables.

Version

2.7.4