feat: factor out advanced_extension logic and add it to other ops

[ingomueller-net]

This PR factors out the handling of the shared_extension field from the plan op and adds that logic to the project op. This mainly consisted of moving the import and export logic from the functions related to the plan op to dedicated functions. The PR also introduces the new ExtensibleOpInterface that enforces an attribute called advanced_extension on the op that implement it and allows to deal with all such ops transparently. Since that interface depends on an attribute, the include order of the generated code of interfaces and attributes also had to be adapted. Unfortunately, the field names in the Substrait spec also vary (singular or plural), so the PR also introduces some template magic to be able to deal with protobuf message types with both spellings. With this PR, message types with an advanced_extension field should be able to support it by (1) adding the ExtensibleOpInterface to their traits, (2) adding an advanced_extension parameter, and (3) adding that parameter to their assembly format (although that's technically optional; otherwise, the attribute is set through the attributes dictionary).