* Moves create_message(), native_invoke() and process_cross_program_instruction()
from the InstructionProcessor to the InvokeContext so that they can have a useful "self" parameter.
* Moves InstructionProcessor into InvokeContext and Bank.
* Moves ExecuteDetailsTimings into its own file.
* Moves Executor into invoke_context.rs
* Moves PreAccount into its own file.
* impl AbiExample for BuiltinPrograms
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