Validate Branch step should allow branch patterns in officialBranches variable

[lbussell]

This check in the Validate Branch step does not work for release/* branches:

docker-tools/eng/common/templates/steps/validate-branch.yml

Lines 14 to 19 in 7841dec

	if ("$(officialBranches)".Split(',').Contains("$(sourceBranch)") `
	-and "$(officialRepoPrefixes)".Split(',').Contains("${{ parameters.publishConfig.publishAcr.repoPrefix }}"))
	{
	echo "Conditions met for official build, continuing..."
	exit 0
	}

We should find a way to allow branch patterns for the officialBranches variable, so that we can treat any release/* branch as an official branch.