Split core logic of app-libs/stf/src/trusted_call.rs into submodules

[clangenb]

We match the trusted call variants and then execute the particular core logic. This is mostly inlined leading to a huge file - it is better to separate them.

[clangenb]

We should use the pattern that we have started for guess the number for instance:

worker/app-libs/stf/src/guess_the_number.rs

Line 86 in 7a6ad96

fn execute(