Add contract verify feature

[codespool]

Overview (What and Why)

cargo-contract now supports verifiable builds, and we should add an option for it too:
https://use.ink/basics/contract-verification/

How

• compile command with --verify (or similar flag) runs a build inside the parity-defined container
• contract verify or similar command submits the deployed address and source files for verification

Definition of Done

• production builds (with opt in/out verification) are running in the predefined container
• new command for verification implemented
• verification status check command implemented
• above changes merged and released
• docs updated

Open Issues and Blockers

• for usage in swanky-dev-container, the docker-in-docker feature should be used, or some kind of parallel containers -> needs investigation

[andabak]

Parity wants to standardize this process so lets understand this impact better before moving forward with this ticket. use-ink/cargo-contract#1065

[HashWarlock]

We use this for our ink! validator function https://github.com/Phala-Network/ink-validator

[codespool]

We use this for our ink! validator function https://github.com/Phala-Network/ink-validator

Oh, nice! ..but what image does it use? I believe we should push the Parity's "official" image as a standard, since it's now published.