Milestone 7: Generate appropriate code, warnings or errors for evm builtins

[xermicus]

The Solidity language has support for assembly statements that can contain evm builtins (evm opcodes), e.g. chainid or create2. For each of the builtin, one of three things need to happen:

1. Generate code for it, like seal_call for call builtin, or generate a constant for chainid builtin
2. Give a useful warning saying this builtin may not work as expected. This should include a link to the documentation
3. Give a useful error saying this builtin may not work as expected. This should include a link to the documentation

The documentation should have a list of all the builtins and how they are handled, and suggestions to solidity developers on how to handle them.

This feature should have tests at

https://github.com/hyperledger-labs/solang/tree/main/integration/substrate

Success means that a pull request has had all its review comments addressed and it is merged.