CI: tools: support per branch tools container

CI: tools: support per branch tools container

Add support to push per branch container tools.
For anything not official stick to latest tag that correspond to test
run from master.

If we are testing something for one of the openwrt stable branch, parse
the branch name or the tag and push dedicated tools containers.

To use the stable container for local testing the branch needs to have
the prefix openwrt-[0-9][0-9].[0-9][0-9] (example openwrt-21.02-fixup)

Any branch that will match this pattern openwrt-[0-9][0-9].[0-9][0-9]
will refresh the tools container with the matching tag.
(example branch openwrt-22.03 -> tools:openwrt-22.03)
(example branch openwrt-22.03-test -> tools:openwrt-22.03)

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>