* Moves stack_height of the instruction_trace into InstructionContext.
* Uses nesting_level instead of stack_height internally in transaction_context.rs
* Uses the instruction_trace instead of the instruction_context_stack internally.
* Adds feature gate: record_instruction_in_transaction_context_push.
* Adds BorrowedAccount::check_sysvar().
* Adds BorrowedAccount::get_data_mut().
* Implements account resizing in BorrowedAccount.
* Exposes is_signer() and is_writable() in InstructionContext.
* Removes AccountMeta and get_instruction_accounts_metas().
* Makes throwing errors in BorrowedAccount optional.
* Removes result return values from BorrowedAccount.
* Replaces from_keyed_account() by SysvarCache in stake instruction.
* Replaces from_keyed_account() by SysvarCache in system instruction processor.
* Removes from_keyed_account().
Moves check_sysvar_keyed_account() into sysvar_cache.rs
* Removes tests which test for incorrectly serialized sysvars.
* 10461 Reject close of vote accounts unless it earned no credits in the previous epoch. This is checked by comparing current epoch (from clock sysvar) with the most recent epoch with credits in vote state.
* Fixup typo
* Add new feature
* Add new TransactionError
* Add framework for checking account state before and after transaction processing
* Fail transactions that leave new rent-paying accounts
* Only check rent-state of writable tx accounts
* Review comments: combine process_result success behavior; log and metrics before feature activation
* Fix tests that assume rent-exempt accounts are okay
* Remove test no longer relevant
* Remove native/sysvar special case
* Move metrics submission to report legacy->legacy rent paying transitions as well
* Makes error handling in BorrowedAccount optional.
Adds BorrowedAccount ::get_rent_epoch().
Exposes InstructionContext::get_index_in_transaction().
Turns accounts and account_keys into pinned boxed slices.
* Introduces "unsafe" to InvokeContext::push().
* Turns &TransactionContext into &mut TransactionContext in InvokeContext.
* Push and pop InstructionContext in InvokeContext.
Makes test_process_cross_program and test_native_invoke symmetric.
Removes the borrow check from test_invoke_context_verify.
* Removes keyed_accounts from prepare_instruction()
* Removes usage of invoke_stack.
* Removes keyed_accounts from program-test.
* Removes caller_write_privileges.
* Removes keyed_accounts from BPF parameter (de-)serialization.
* Add more-legitimate conversion from legacy Transaction to SanitizedTransaction
* Add Banks method with preflight checks
* Expose BanksClient method with preflight checks
* Unwrap simulation err
* Add Bank simulation method that works on unfrozen Banks
* Add simpler api
* Better name: BanksTransactionResultWithSimulation
* Adds TransactionContext, InstructionContext and BorrowedAccount.
* Redirects the usage of accounts in InvokeContext through TransactionContext.
Also use the types declared in transaction_context.rs everywhere.
* Adjusts all affected tests.
