Gradle Build: Solidity support

[jjohannes]

Breakdown as discussed with @david-bakin-sl.

1. Generate bin and json from sol in https://github.com/hashgraph/hedera-services/tree/develop/hedera-node/test-clients/src/main/resource/contract/contracts - bin and json are no longer checked in; sol do not need to be in resources (not needed at runtime); may use org.web3j.solidity Gradle plugin.
2. Get System Contracts sol from from https://github.com/hashgraph/hedera-smart-contracts instead of maintaining a copy in hedera-services.
3. Only System Contracts: generate Java code based on them in hedera-smart-contract-service-impl

[jjohannes]

Additional Notes:

we need to run with different solitity compiler versions, and we need to be able to say, in the gradle build file, which compiler version we want (if not the most recent), for specific contracts. We also need to be able to override, in the build file, the EVM version to build for. (Needn't be in the build file if it was acceptable/preferable to have an additional file of these configurations sitting around, perhaps at the root of the directory tree of the contracts being built.)

Reason is - second first. Around the time of EVM changes (e.g., in April just before/after they released the Cancun version that had additional opcodes and changed some opcode behavior) we need to test before/after - that is, that contracts written for Cancun fail on the previous release, that contracts written for the previous release have changed behavior for the new release.

First reason: Solitity changes and (frequently, unfortunately) in not backward compatible ways. So you sometimes have contracts that used to work with a previous Solidity version that are compiled differently and incompatibly now. You need to compile them with a suitable compiler. Solidity even has a pragma that every source file must start with that gives the range of acceptable compiler versions.

But those two reasons are exceptions. Nearly all contracts you compile with the latest compiler and latest EVM version.

[jjohannes]

Duplicate of #7456