Make message sending from programs more frequent

[techraed]

Problem to Solve

Cover more runtime code areas that are related to message sending (in gas tree, in Externalities impl, in pallet_gear::internal)

Possible Solution

That task requires some research and running fuzzer frequently. Some possible solutions:

1. Insert Send* type calls in gear exports
2. Change config so calls become really frequent (when there less functions, or less instructions number). Related issues #3313 (working on it in #3391)