add: CI_REGISTRY_BUILD_CONTEXT variable

Allows to set the build context to a different directory with a default of the working directory.

requested review from @sheogorath

assigned to @w4tsn

This needs a rebase for 2.0.0

added 37 commits

• 46231359...d9e2a258 - 36 commits from branch main
• d49a852c - add: CI_REGISTRY_BUILD_CONTEXT variable

Compare with previous version

merged

mentioned in commit 901d62eb