Anchor IDL should include all accounts required

[seanyoung]

Right now, when writing anchor client code or when doing a CPI in Solidity, the accounts must be specified. This is difficult to figure out.

• The system account and clock account should be automaticallly included in the list, if the functions or any function it calls (transitively) uses the system/clock acount. #1191
• Any account required by calling another contract should be included and possibly populated automatically. If it cannot be populated automatically, then the signer/writable flags should be populated automatically
• Improving Solana account management #1251
• When importing IDL files using solang idl the accounts should be put into annotations and in the IDL.