Avoid untested Rust code

[ma2bd]

Rust code blocks that could go out of sync should be either tested (i.e. type-checked in this case) or reduced to a single "include" of a piece of code from linera-protocol (or elsewhere, as long as it is tested).

• Avoid untested Rust code in src/developers/sdk/abi.md #175
• Avoid untested Rust code in src/developers/sdk/composition.md #176
• Avoid untested Rust code in src/developers/sdk/contract.md #177
• Avoid untested Rust code in src/developers/sdk/messages.md #178
• Avoid untested Rust code in src/developers/sdk/service.md #179
• Avoid untested Rust code in src/developers/sdk/state.md #180
• Avoid untested Rust code in src/developers/sdk/testing.md #181
• Avoid untested Rust code in src/developers/advanced_topics/assets.md #182
• Avoid untested Rust code in src/developers/advanced_topics/contract_finalize.md #183
• Avoid untested Rust code in src/developers/experimental/ml.md #184