Add program abstraction, including object interfaces and transaction protocol objects (in the sense of https://doi.org/10.1145/3527324)

[heindel]

The paper introduces in §8 the notion of transactional protocol object, after introducing two very natural concepts

• programs over an (object) interface such that
• a single (derived) ?exec method take these programs as argument

This would then directly provide the abstraction, as discussed here (in the context of the ART-TRMO). A detail that deserves attention is whether and how the possibility to abort execution of programs is to be handled in a gas metered setting.

[heindel]

This is addressed in Definition 4 and the surrounding section.