Citus Package Improvements

[gurkanindibay]

• packaging_encryption key packaging_passphrase variables are optional especially for community packages. These parameter should be validated according to thier enterprise/comminty nature and if it is not needed, it should not be mandatory
• default value for gh_token variable should be environment variable with the same name
• There should be a summary section which summarizes all of the warnings and ignored warnings at the end of the build