Cross-program invocation.
Solana programs may call other programs, termed [_cross-program
invocations_][cpi] (CPI), with the [`invoke`] and [`invoke_signed`]
functions.
This crate does not support overwriting syscall stubs for offchain code.
If you want to overwrite syscall stubs, use the wrapper functions in
[`solana_program::program`].
[`invoke`]: invoke
[`invoke_signed`]: invoke_signed
[cpi]: https://solana.com/docs/core/cpi
[`solana_program::program`]: https://docs.rs/solana-program/latest/solana_program/program/