Deprecate old methods

[tiago18c]

Deprecate old methods when v1.9 goes live according to:

https://docs.solana.com/developing/clients/jsonrpc-api#json-rpc-api-deprecated-methods

[hoakbuilds]

Need to add:

• getFeeForMessage
• getHighestSnapshotSlot

Need to deprecate:

• getSnapshotSlot
• getFeeCalculatorForBlockhash
• getFeeRateGovernor
• getFees