* SDK: Split new `FeeRateGovernor` out of `FeeCalculator`
Leaving `FeeCalculator` to *only* calculate transaction fees
* Replace `FeeCalculator` with `FeeRateGovernor` as appropriate
* Expose recent `FeeRateGovernor` to clients
* Move `burn()` back into `FeeCalculator`
Appease BPF tests
* Revert "Move `burn()` back into `FeeCalculator`"
This reverts commit f3035624307196722b62ff8b74c12cfcc13b1941.
* Adjust BPF `Fee` sysvar test to reflect removal of `burn()` from `FeeCalculator`
* Make `FeeRateGovernor`'s `lamports_per_signature` private
* rebase artifacts
* fmt
* Drop 'Recent'
* Drop _with_commitment variant
* Use a more portable integer for `target_signatures_per_slot`
* Add docs for `getReeRateCalculator` JSON RPC method
* Don't return `lamports_per_signature` in `getFeeRateGovernor` JSONRPC reply
* Add num_readonly_accounts slice
* Impl programs in account_keys
* Emulate current account-loading functionality using program-account_keys (breaks exchange_program_api tests)
* Fix test
* Add temporary exchange faucet id
* Update chacha golden
* Split num_credit_only_accounts into separate fields
* Improve readability
* Move message field constants into Message
* Add MessageHeader struct and fixup comments
