refactor: reorganize project

[nxsaken]

Description

This fixes the error with cargo install:

package `.../client/tests/integration/smartcontracts/executor_custom_data_model/Cargo.toml` is a member of the wrong workspace

• move all binary crates to /bins
• move all library crates to /libs
• move executors, smart contracts and triggers to /samples
• unnest iroha_executor and iroha_trigger from iroha_smart_contract
• rename crate directories to match their actual names (except nested utility crates)

Benefits

• binaries can be installed with cargo install
• separation between binaries and libraries
• more predictable structure and names

Checklist

• I've read CONTRIBUTING.md
• I've used the standard signed-off commit format (or will squash just before merging)
• All applicable CI checks pass (or I promised to make them pass later)
• (optional) I've written unit tests for the code changes
• I replied to all comments after code review, marking all implemented changes with thumbs up

[mversic]

I think you should break this into several PRs

[Erigara]

can this error be fixed in less invasive way?

[nxsaken]

Superseded by #4863.